docs: def init_app(self, app):
          """Flask application initialization."""
          self.init_config(app)
          self.iiif_ext = IIIF(app=app)
          self.iiif_ext.api_decorator_handler(protect_api)
          self.iiif_ext.uuid_to_image_opener_handler(image_opener)
          app.extensions['invenio-iiif'] = self