The apple developer webapp consistently refers this App ID. So,
this clears any confusion that can occur.
Since python social auth only requires us to include App ID in
_AUDIENCE(a list), we do that in computed settings making it easier for
server admin and we make it much clear by having it set to
APP_ID instead of BUNDLE_ID.
This implementation overrides some of PSA's internal backend
functions to handle `state` value with redis as the standard
way doesn't work because of apple sending required details
in the form of POST request.
Includes a mixin test class that'll be useful for testing
Native auth flow.
Thanks to Mateusz Mandera for the idea of using redis and
other important work on this.
Documentation rewritten by tabbott.
Co-authored-by: Mateusz Mandera <mateusz.mandera@zulip.com>
Anders Kaseorg
Mateusz Mandera
Dinesh