Pending Invitation Not Cancelled When User Deleted via SCIM

Summary

When a user is deleted via SCIM before they have accepted their invitation, the pending invitation remains active. The deleted user can still accept the invitation and join the team. The user appears as an active team member but is unable to log in to Wire. This is primarily a visual bug — the user shows up in the team roster but is functionally inaccessible.

Expected behavior

When a SCIM DELETE request is received for a user, any pending invitation associated with that user should be automatically cancelled. The user should not appear as an active team member after deletion, and no invitation should remain that could allow re-joining.

Actual behavior

1. User is created and an invitation is sent (user has not accepted yet)
2. User is deleted via SCIM DELETE /Users/{id}
3. The pending invitation remains active in the system
4. The user can accept the invitation and is added back as an active team member
5. The user appears in the team roster but cannot log in to Wire

Start at the SCIM DELETE /Users/{id} handler and trace how pending invitations are handled when a user is removed. Reproduce the sequence described in the issue, then verify that deletion cancels the pending invitation and prevents the user from reappearing through invitation acceptance.