This removes the last remaining code that called out to the
cs_comments_service. All forums backend logic now uses the v2 API from
the forum repo (https://github.com/openedx/forum). This does NOT remove
MongoDB support.
This also implements the endpoint to retrieve all comments for a user
using the new forum backend. This is not actually called from any known
frontend code, but it has not been formally deprecated as an endpoint,
and therefore needs to be supported.
As part of the cleanup, the ENABLE_FORUM_V2 course waffle flag has also
been removed, along with all remaining switching logic that used to
route between the Python API in the forum repo and service calls to the
cs_comments_service Ruby service.
Other endpoints affected (switching logic removed):
* get course commentable counts
* get/update course user stats
* update comment/thread/user
* delete thread (implementation moved to forum repo)
* follow
* retire user
This is part of the following overall DEPR ticket:
https://github.com/openedx/cs_comments_service/issues/437
4c051378d0