R1:649f8827205a

Slightly modernize all Diffusion edit endpoints

Summary: Ref T4245. Prepares edit endpoints for more flexible repository identifiers.

Test Plan:
- Added, edited, deleted mirror.
- Created repository.
- Edited basic repository information.
- Edited policies for a repository.
- Activated/deactivated repository.
- Updated a repository.
- Hit "Delete" dialog for a repository.
- Edited hosting.
- Toggled dangerous changes.
- Edited branches.
- Edited automation.
- Tested automation.