Ths hardcoded documentation of which values are possible was destined
to end up inaccurate and out-of-date; and meanwhile, we do have a part
of the API that already has these data in machine-readable format.
This commit adds a server level setting which controls whether the setting
can be set to anonymous user groups. We only allow it in the tests for
now because the UI can only handle named user groups.
This commit adds support to pass object containing both old and new
values of the can_mention_group setting, as well as detailed API
documentation for this part of the API system.
Co-authored-by: Tim Abbott <tabbott@zulip.com>
Co-authored-by: Greg PRice <greg@zulip.com>
