support for SSO via twitter

[richvdh]

Twitter use OAuth1, so this is a pain.

[clokep]

Twitter use OAuth1, so this is a pain.

Note that Twitter does support OAuth 2.0 now:

• https://developer.twitter.com/en/docs/authentication/oauth-2-0/user-access-token
• https://developer.twitter.com/en/docs/authentication/oauth-2-0/authorization-code

We need some changes on our side to handle it (mostly RFC7636 support). I'll take a look at this.

[clokep]

This also has the same issues as #8511 where the userinfo endpoint puts everything under a data map.