Implemented by having Discourse download the image from the provided URL
and treating it as a custom upload.
Adds two more parameters to the SSO site’s response:
* `avatar_url` specifies the URL of the overriding avatar.
* `avatar_force_update` Discourse does not re-download avatars that
has already been download from the same URL. Setting this to true forces
Discourse to re-download the avatar in `avatar_url`
Note that both parameters are ignored if `sso_overrides_avatar` is set
to false.
add an external_username attribute for username from SSO payload
repair the field name in SingleSignOnRecord migration
move setting of external_username for sso to controller
add settings toggle to override username/email from SSO payload
fix changing of external username after override toggle
complete tests and logic for sso override
add some extra context to username override option
add external_email and external_name to single sign on record
add setting for name override from SSO payload
complete override with stored external_email and external_name
add missing checks to tests
remove an unneeded describe block
break up a monster method for single sign on
fixes for sso attribute override after failed tests
