feat: support mautrix bridgev2 / megabridge APIs

[ignyx]

New versions of the mautrix go bridges include standardized HTTP endpoints that can be used to log in and manage sessions (spec). Some clients may choose to provide interfaces. At this time, mautrix-manager can consume these endpoints. An auto-discovery .well-known file can be set.

This PR aims to make these endpoints public and setup auto-discovery.

Please let me know :

• whether this can be useful
• whether the mautrix-messenger implementation is acceptable, to serve as a baseline for the next bridges
• any recommendations

[spantaleev]

This looks good!

How does authentication work?

Have you got mautrix-manager working and successfully accessing the Messenger bridge's bridgev2 API?

[ignyx]

Thanks for the reply !

How does authentication work?

• For local bridges on same homeserver: the Matrix Access Token is sent with requests to the bridgev2 API
• For external bridges: "the manager will generate an OpenID token and exchange it for a temporary bridge-specific auth token rather than sending your Matrix access token to the bridge." (from mautrix/manager readme)

Have you got mautrix-manager working and successfully accessing the Messenger bridge's bridgev2 API?

Yes !

Note: to read log outputs from mautrix/manager I had to clone the repo and yarn start, then check the console output from the devtools. Logs are not output to stdout.

I will work on adding supported bridges.