Support for stable version of MSC3824 OAuth 2.0 aware

[hughns]

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

• Support for stable OAuth 2.0 API discovery with fallback to unstable MSC2965 .well-known
  • Uses the /_matrix/client/v1/auth_metadata endpoint if available.
• Where server supports auth_metadata, then support for stable action parameter from MSC4191
  • Uses account_management_actions_supported discovery to choose the stable or unstable MSC4191 action parameters passed to account_management_uri.
• Support for stable oauth_aware_preferred flag on m.login.sso auth flow from MSC3824
• Send stable action parameter on SSO redirect from MSC3824

Motivation and context

Screenshots / GIFs

Tests

• Step 1
• Step 2
• Step ...

Tested devices

• Physical
• Emulator
• OS version(s):

Checklist

• Changes has been tested on an Android device or Android emulator with API 21
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/element-hq/element-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request includes a new file under ./changelog.d. See https://github.com/element-hq/element-android/blob/develop/CONTRIBUTING.md#changelog
• Pull request includes screenshots or videos if containing UI changes
• Pull request includes a sign off
• You've made a self review of your PR
• If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()

Signed-off-by: Hugh Nimmo-Smith hughns@element.io

[hughns]

I'm not sure what the linter is complaining about, it appears to be something outside of the changes in this PR. Otherwise, I think this is ready for full review.