Modify the way we're doing OAuth for C2S to support the flows of IndieAuth.
Some simplified docs at oauth.com: https://www.oauth.com/oauth2-servers/indieauth/
I need to go over some documentation related to it, and its differences with other authentication mechanisms:
vs. OpenID: https://indieweb.org/How_is_IndieAuth_different_from_OpenID_Connect
The docs for the authorization end-point is: https://indieweb.org/authorization-endpoint
An example of login with IndieAuth: https://pin13.net/login/
An example of a IndieAuth login request is:
/oauth/authorize?me=https://brutalinks.tech/~marius&redirect_uri=https://indielogin.com/redirect/indieauth&client_id=https://indielogin.com/&state=7e2f1297a2891169dafe13bc&response_type=id
I added the authorization flow in e403640b