Server Tests: Interview Management Endpoints

[Abi107717]

Write comprehensive server-side tests for new interview management endpoints (delete slot, add interviewees, get interviewees).

1. DELETE /api/interviews/slots/{slotId}

• Delete unbooked slot → 204 No Content
• Delete booked slot → 400 Bad Request (cannot delete booked)
• Delete slot from other professor → 403 Forbidden
• Delete non-existent slot → 404 Not Found
• Verify slot is actually removed from database

2. POST /api/interviews/processes/{processId}/interviewees

• Add valid applicants → 201 Created, returns IntervieweeDTOs
• Add applicants from different job → 400 Bad Request
• Add duplicate applicants → skip duplicates silently, no error
• Add as non-owner → 403 Forbidden
• Add to non-existent process → 404 Not Found
• Verify interviewees created in database
• Verify correct state ("UNCONTACTED" initially)

3. GET /api/interviews/processes/{processId}/interviewees

• Get all interviewees → returns full list
• Get as non-owner → 403 Forbidden
• Get from non-existent process → 404 Not Found
• Verify state calculation (based on lastInvited and slots)