Repository transfer has to be confirmed, if user can not create repo for new owner (#14792)

* make repo as "pending transfer" if on transfer start doer has no right to create repo in new destination

* if new pending transfer ocured, create UI & Mail notifications

models/models.go

@@ -133,6 +133,7 @@ func init() {
 		new(ProjectBoard),
 		new(ProjectIssue),
 		new(Session),
+		new(RepoTransfer),
 	)
 
 	gonicNames := []string{"SSL", "UID"}