I'm wondering why the server metadata URL for an OAuth2Mixin (e.g. for DjangoOAuth2App) starts with an _ (_server_metadata_url) since this usually denotes that the attribute should not be accessible outside of the class itself. There's also no helper property to get and set the server_metadata_url. What's the reasoning behind this design decision?

An example use case that I can think of that would benefit from a helper function to set server_metadata_url: The server metadata URL is something specified by a user in an application. The metadata URL differs based on environment (pre-prod vs prod). If the user specifies the incorrect metadata URL and corrects this, the application would update the metadata URL of the oauth client instead of re-registering a new backend.