Modules system: callback for on_login which includes the deviceName from the client

[benparsons]

I'm looking at https://matrix-org.github.io/synapse/develop/modules.html and don't see a callback for on_login. I'd like a callback that contains the deviceName for the user logging in.

cc @babolivier @chagai95

[babolivier]

Will be fixed by porting the auth provider module interface to the new one (tracked as part of #10469)

[clokep]

Note that you can do this already with password auth providers: https://matrix-org.github.io/synapse/develop/password_auth_providers.html

When porting to the new module system (#10469) we should probably make this particular callback not dependent on being related to password providers. (I.e. why not have this for an SSO user too?)

[anoadragon453]

I don't think any of the password auth provider callbacks will help here if a user is logging in via the m.login.password User-Interactive Authentication type (which is often used) or via SSO.

1. Registering a check_auth callback does not allow you to override m.login.password nor m.login.sso.
2. check_3pid_auth will only fire if a user logs in with a third-party ID (email or phone number), which also does not work for password or SSO logins.

Therefore I think we still need a on_user_login callback which provides:

1. The user's Matrix ID.
2. The login type (m.login.password, m.login.sso).
3. This device's ID.

We could then add another Module API method that allows modules to get the displayname of a device given the ID.

Putting it under the Account Validity callbacks (next to on_user_registration) makes the most sense to me.