docs: def init_app(self, app, client_id=None):
          """Initialize the Micropub extension if it was not given app
          in the constructor.
  
          Args:
            app (flask.Flask): the flask application to extend.
            client_id (string, optional): the IndieAuth client id, will be
              displayed when the user is asked to authorize this client. If not
              provided, the app name will be used.
          """
          if not self.client_id:
              if client_id:
                  self.client_id = client_id
              else:
                  self.client_id = app.name