feat(workspace): add accept and decline invitation use cases

- Implement AcceptInvitationUseCase with validation
- Check invitation status, expiration, and email match
- Auto-create WorkspaceMember on accept
- Handle case when user is already a member
- Implement DeclineInvitationUseCase to reject invitations
- Update invitation status (accepted/declined/expired)
- Add 9 comprehensive unit tests (all passed)

Phase 4 Task 14/68 completed

tests/unit/test_accept_invitation_use_case.py

@@ -0,0 +1,315 @@
+"""
+接受/拒绝邀请 Use Case 测试
+"""
+import pytest
+from unittest.mock import Mock
+from datetime import datetime, timedelta, timezone
+from packages.application.workspace.accept_invitation_use_case import (
+    AcceptInvitationUseCase,
+    AcceptInvitationRequest,
+    DeclineInvitationUseCase,
+    DeclineInvitationRequest,
+)
+from packages.domain.entities import (
+    Workspace,
+    WorkspaceInvitation,
+    WorkspaceMember,
+    User,
+    InvitationStatus,
+)
+
+
+class TestAcceptInvitationUseCase:
+    """接受邀请测试"""
+    
+    @pytest.fixture
+    def mock_workspace_repo(self):
+        repo = Mock()
+        repo.find_by_id = Mock(return_value=None)
+        return repo
+    
+    @pytest.fixture
+    def mock_member_repo(self):
+        repo = Mock()
+        repo.find_by_workspace_and_user = Mock(return_value=None)
+        repo.save = Mock()
+        return repo
+    
+    @pytest.fixture
+    def mock_invitation_repo(self):
+        repo = Mock()
+        repo.find_by_token = Mock(return_value=None)
+        repo.save = Mock()
+        return repo
+    
+    @pytest.fixture
+    def mock_user_repo(self):
+        repo = Mock()
+        repo.find_by_id = Mock(return_value=None)
+        return repo
+    
+    @pytest.fixture
+    def use_case(self, mock_workspace_repo, mock_member_repo, mock_invitation_repo, mock_user_repo):
+        return AcceptInvitationUseCase(
+            workspace_repository=mock_workspace_repo,
+            workspace_member_repository=mock_member_repo,
+            workspace_invitation_repository=mock_invitation_repo,
+            user_repository=mock_user_repo,
+        )
+    
+    @pytest.fixture
+    def test_workspace(self):
+        return Workspace(
+            id="workspace-123",
+            name="Test Workspace",
+            owner_user_id="owner-id",
+        )
+    
+    @pytest.fixture
+    def test_user(self):
+        return User(
+            id="user-123",
+            email="invitee@test.com",
+            username="invitee",
+            display_name="Invitee User",
+        )
+    
+    @pytest.fixture
+    def valid_invitation(self):
+        return WorkspaceInvitation(
+            id="invitation-1",
+            workspace_id="workspace-123",
+            inviter_user_id="inviter-id",
+            invitee_email="invitee@test.com",
+            role="member",
+            invitation_token="valid-token",
+            status=InvitationStatus.PENDING,
+            expires_at=datetime.now(timezone.utc) + timedelta(days=7),
+        )
+    
+    def test_accept_invitation_success(
+        self,
+        use_case,
+        mock_workspace_repo,
+        mock_member_repo,
+        mock_invitation_repo,
+        mock_user_repo,
+        test_workspace,
+        test_user,
+        valid_invitation,
+    ):
+        """测试接受邀请成功"""
+        mock_invitation_repo.find_by_token.return_value = valid_invitation
+        mock_user_repo.find_by_id.return_value = test_user
+        mock_workspace_repo.find_by_id.return_value = test_workspace
+        mock_member_repo.find_by_workspace_and_user.return_value = None
+        
+        request = AcceptInvitationRequest(
+            invitation_token="valid-token",
+            user_id="user-123",
+        )
+        
+        response, error = use_case.execute(request)
+        
+        assert error is None
+        assert response is not None
+        assert response.workspace_id == "workspace-123"
+        assert response.workspace_name == "Test Workspace"
+        assert response.role == "member"
+        
+        # 验证创建了成员记录
+        mock_member_repo.save.assert_called_once()
+        member = mock_member_repo.save.call_args[0][0]
+        assert member.user_id == "user-123"
+        assert member.role == "member"
+        assert member.invited_by == "inviter-id"
+        
+        # 验证更新了邀请状态
+        assert valid_invitation.status == InvitationStatus.ACCEPTED
+        assert valid_invitation.accepted_at is not None
+    
+    def test_accept_invitation_invalid_token(self, use_case, mock_invitation_repo):
+        """测试无效令牌"""
+        mock_invitation_repo.find_by_token.return_value = None
+        
+        request = AcceptInvitationRequest(
+            invitation_token="invalid-token",
+            user_id="user-123",
+        )
+        
+        response, error = use_case.execute(request)
+        
+        assert response is None
+        assert error == "Invalid invitation token"
+    
+    def test_accept_invitation_already_accepted(
+        self,
+        use_case,
+        mock_invitation_repo,
+        valid_invitation,
+    ):
+        """测试邀请已被接受"""
+        valid_invitation.status = InvitationStatus.ACCEPTED
+        mock_invitation_repo.find_by_token.return_value = valid_invitation
+        
+        request = AcceptInvitationRequest(
+            invitation_token="valid-token",
+            user_id="user-123",
+        )
+        
+        response, error = use_case.execute(request)
+        
+        assert response is None
+        assert error == "Invitation has already been accepted"
+    
+    def test_accept_invitation_expired(
+        self,
+        use_case,
+        mock_invitation_repo,
+        valid_invitation,
+    ):
+        """测试邀请已过期"""
+        valid_invitation.expires_at = datetime.now(timezone.utc) - timedelta(days=1)
+        mock_invitation_repo.find_by_token.return_value = valid_invitation
+        
+        request = AcceptInvitationRequest(
+            invitation_token="valid-token",
+            user_id="user-123",
+        )
+        
+        response, error = use_case.execute(request)
+        
+        assert response is None
+        assert error == "Invitation has expired"
+        assert valid_invitation.status == InvitationStatus.EXPIRED
+    
+    def test_accept_invitation_email_mismatch(
+        self,
+        use_case,
+        mock_invitation_repo,
+        mock_user_repo,
+        valid_invitation,
+    ):
+        """测试邮箱不匹配"""
+        mock_invitation_repo.find_by_token.return_value = valid_invitation
+        
+        different_user = User(
+            id="user-123",
+            email="different@test.com",
+            username="different",
+            display_name="Different User",
+        )
+        mock_user_repo.find_by_id.return_value = different_user
+        
+        request = AcceptInvitationRequest(
+            invitation_token="valid-token",
+            user_id="user-123",
+        )
+        
+        response, error = use_case.execute(request)
+        
+        assert response is None
+        assert error == "This invitation is for a different email address"
+    
+    def test_accept_invitation_already_member(
+        self,
+        use_case,
+        mock_workspace_repo,
+        mock_member_repo,
+        mock_invitation_repo,
+        mock_user_repo,
+        test_workspace,
+        test_user,
+        valid_invitation,
+    ):
+        """测试用户已经是成员"""
+        mock_invitation_repo.find_by_token.return_value = valid_invitation
+        mock_user_repo.find_by_id.return_value = test_user
+        mock_workspace_repo.find_by_id.return_value = test_workspace
+        
+        existing_member = WorkspaceMember(
+            id="member-1",
+            workspace_id="workspace-123",
+            user_id="user-123",
+            role="admin",
+        )
+        mock_member_repo.find_by_workspace_and_user.return_value = existing_member
+        
+        request = AcceptInvitationRequest(
+            invitation_token="valid-token",
+            user_id="user-123",
+        )
+        
+        response, error = use_case.execute(request)
+        
+        assert error is None
+        assert response is not None
+        assert response.role == "admin"  # 返回现有角色
+        
+        # 不创建新成员记录
+        mock_member_repo.save.assert_not_called()
+        
+        # 但仍标记邀请为已接受
+        assert valid_invitation.status == InvitationStatus.ACCEPTED
+
+
+class TestDeclineInvitationUseCase:
+    """拒绝邀请测试"""
+    
+    @pytest.fixture
+    def mock_invitation_repo(self):
+        repo = Mock()
+        repo.find_by_token = Mock(return_value=None)
+        repo.save = Mock()
+        return repo
+    
+    @pytest.fixture
+    def use_case(self, mock_invitation_repo):
+        return DeclineInvitationUseCase(
+            workspace_invitation_repository=mock_invitation_repo,
+        )
+    
+    @pytest.fixture
+    def valid_invitation(self):
+        return WorkspaceInvitation(
+            id="invitation-1",
+            workspace_id="workspace-123",
+            inviter_user_id="inviter-id",
+            invitee_email="invitee@test.com",
+            role="member",
+            invitation_token="valid-token",
+            status=InvitationStatus.PENDING,
+            expires_at=datetime.now(timezone.utc) + timedelta(days=7),
+        )
+    
+    def test_decline_invitation_success(self, use_case, mock_invitation_repo, valid_invitation):
+        """测试拒绝邀请成功"""
+        mock_invitation_repo.find_by_token.return_value = valid_invitation
+        
+        request = DeclineInvitationRequest(invitation_token="valid-token")
+        success, error = use_case.execute(request)
+        
+        assert success is True
+        assert error is None
+        assert valid_invitation.status == InvitationStatus.DECLINED
+    
+    def test_decline_invitation_invalid_token(self, use_case, mock_invitation_repo):
+        """测试无效令牌"""
+        mock_invitation_repo.find_by_token.return_value = None
+        
+        request = DeclineInvitationRequest(invitation_token="invalid-token")
+        success, error = use_case.execute(request)
+        
+        assert success is False
+        assert error == "Invalid invitation token"
+    
+    def test_decline_invitation_already_accepted(self, use_case, mock_invitation_repo, valid_invitation):
+        """测试邀请已被接受"""
+        valid_invitation.status = InvitationStatus.ACCEPTED
+        mock_invitation_repo.find_by_token.return_value = valid_invitation
+        
+        request = DeclineInvitationRequest(invitation_token="valid-token")
+        success, error = use_case.execute(request)
+        
+        assert success is False
+        assert error == "Invitation has already been accepted"