- Implement InviteMemberUseCase with role-based permission check
- Only owner/admin can invite members (not regular members)
- Cannot invite as owner (owner is unique per workspace)
- Check for duplicate invitations and existing members
- Generate invitation token with 7-day expiration
- Send invitation email with accept link
- Add 7 comprehensive unit tests (all passed)
Phase 4 Task 13/68 completed
Xiaoxia AI
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