Move AddCollabrator and CreateRepositoryByExample to service layer (#32419)

- [x] Move `CreateRepositoryByExample` to service layer
- [x] Move `AddCollabrator` to service layer
- [x] Add a new parameter for `AddCollabrator` so that changing mode
immediately after that will become unnecessary.

Author: lunny

models/perm/access_mode.go

@@ -60,3 +60,6 @@ func ParseAccessMode(permission string, allowed ...AccessMode) AccessMode {
 	}
 	return util.Iif(slices.Contains(allowed, m), m, AccessModeNone)
 }
+
+// ErrInvalidAccessMode is returned when an invalid access mode is used
+var ErrInvalidAccessMode = util.NewInvalidArgumentErrorf("Invalid access mode")