Consider Cascade Delete on Admin Deletion

[krapie]

Description:

Following the recent introduction of the feature to delete admin users in #934, it is crucial to consider implementing a cascade delete mechanism for admin-related resources such as projects, documents, and changes.

Why:

Currently we only allows the deletion of admin users without any cascading effect on related resources, potentially resulting in orphan resources beyond the control of the admin. To ensure better resource management and data consistency, the introduction of cascade delete functionality is essential.

[Wu22e]

Can I proceed with this issue?

[krapie]

@Wu22e Sure!