Separate webfinger domain from host domain
This addresses the first part of #201 (closed)
The existing Pleroma.Web.Endpoint host config is equivalent to Mastodon's WEB_DOMAIN. This adds a new config option under Pleroma.Web.Endpoint called domain that is equivalent to Mastodon's LOCAL_DOMAIN.
This PR also modifies webfinger to:
- Return the same data for username @ WEB_DOMAIN and for username @ LOCAL_DOMAIN
Resolving username @ WEB_DOMAIN is necessary because AP servers will use that domain for look up in some situations.
- Return username @ LOCAL_DOMAIN as the Subject for both JSON and XML response formats.
This appears to be the field that Mastodon uses to populate user handles.