OIDC: Log in (#3554)
* use oidc-client-ts during oidc discovery
* export new type for auth config
* deprecate generateAuthorizationUrl in favour of generateOidcAuthorizationUrl
* testing util for oidc configurations
* test generateOidcAuthorizationUrl
* lint
* test discovery
* dont pass whole client wellknown to oidc validation funcs
* add nonce
* use oidc-client-ts for oidc response
* validate user state and update tests
* use oidc-client-ts for code exchange
* use oidc-client-ts in completing auth grant
* use client userState for homeserver
* more comments
