Adds shared_with_user and shared_with_group filters to the /workspaces
endpoint.
- `shared_with_user`: filters workspaces shared with a specific user.
Accepts a user UUID or username.
- `shared_with_group`: filters workspaces shared with a specific group.
Accepts:
- a group UUID, or
- `<organization name>/<group name>`, or
- `<group name>` (resolved in the default organization).
Closes
[coder/internal#1004](https://github.com/coder/internal/issues/1004)