Update source docs with new property mappings

With #8771, it is now possible to get additional properties from an OAuth and SAML source, plus getting groups and syncing those. We need to update our sources documentation with those changes. As some of those docs are community supported, I'm opening this issue to ping whomever made recent changes to those if they want to update them with the new (and recommended) way of getting that data. Those changes will make it in 2024.8, so it may be a bit difficult to try things out just yet, but the currently documented way of getting data will still work until the documentation can be changed.

Documentation for those changes is available in #10652 (see the authentik-docs comment for the preview link). Please link back to this issue if you open a PR for those.

• AzureAD - @tograss
• Discord - authentik support level, but we've seen a lot of contribution on this so - @Keyinator @Aterfax
• GitHub - authentik support level, but we've seen a lot of contribution on this so - @TheMythologist
• Google - community supported