feat: reimagine certificate display settings
The course settings `certificate_available_date` (CAD) and
`certificates_display_behavior` (CDB) were previously
acting indedependantly of one another. They now work in
tandem. This change:
- limits CDB to a dropdown
- removes "early_with_info" and adds "end_with_date"
- only takes CAD into account if "end_with_date" is selected
- Moves CDB to the main course schedule settings page
- updates CourseOverview model and CourseDetails objects to
validate these fields and choose sane defaults if they aren't
expected values
This work was previously done in bd9e7dd (complete with bugs), so this
version is toggleable via the ENABLE_V2_CERT_DISPLAY_SETTINGS setting
The `may_certify` function is used to determine whether a learner should
be able to see that their certificate is ready. It is therefore entirely
in the certificates domain. This remove may_certifiy and
may_certify_for_course from the xmodule and course_overview
apps and into the certificates app. The xmodule may_certify was not called
outside of tests prior to this, and the other's were easily moved.
In order to avoid circular imports, this also moved
certificate_info_for_user out of the model code and into an API
[MICROBA-1208]
* consolidate `has_html_certificates_enabled` and `has_html_certificates_enabled_from_course_overview`, the latter of the two functions was created for use during our transition away from using the modulestore in the certificate app.
[MICROBA-1178]
- remove modulestore usage in `generation_handler.py`
- add duplicate functions that utilize a CourseKey or CourseOverview to remove dependence on modulestore (this will be cleaned up (if possible) at a later part of this refactor)
- add python API function to `content`/`course_overview` app that will retrieve a single CourseOverview (rather than a serialized list of dicts of CourseOverview data)
