Pass user to sharing/delete API endpoint

In the recommended storage hook for git integration no user gets passed when deleting a shared collection. The user is "Anonymus". This passes the owner name to the storage hook.

radicale/sharing/__init__.py

@@ -1223,7 +1223,8 @@ class BaseSharing:
             if user == share['Owner']:
                 result = self.database_delete_sharing(
                        ShareType=ShareType,
-                       PathOrToken=PathOrToken) # verification above that it is not None
+                       PathOrToken=PathOrToken,
+                       User=share['Owner']) # verification above that it is not None
             else:
                 # only owner is permitted to delete a share
                 logger.warning(api_info + ": %r not permitted for user %r", PathOrToken, user)