[TSD] [SE-3990] Add in standardized documentation for Badgr-related settings.

This ticket adds standardized annotations to settings related to OpenBadges and Badgr-server.

*JIRA tickets*: https://openedx.atlassian.net/browse/OSPR-5562

*Discussions*: https://edx.readthedocs.io/projects/edx-installing-configuring-and-running/en/latest/configuration/enable_badging.html

*Dependencies*: None

*Merge deadline*: None

*Author notes and concerns*:

This PR documents all of the settings mentioned in https://docs.google.com/spreadsheets/d/1xWbEL6oNu6D84WKBs3aViLRM40xk-vmnmmGAeLyR09A/edit?ts=6008a109#gid=0 However, there are additional settings in https://docs.google.com/spreadsheets/d/1xWbEL6oNu6D84WKBs3aViLRM40xk-vmnmmGAeLyR09A/edit?ts=6008a109#gid=0 which include not only a model which inherits from ConfigurationModel, but also a model that appears to be for configuration, but which does NOT inherit from ConfigurationModel.

I wish I could tell you why I made it that way, but that was in 2015. It may have just been an oversight.

I'm curious if we should go ahead and do these now or if any other changes would need to be done to them first. For instance I don't know if the linting tools we have would recognize or know what to do with the model which doesn't inherit from ConfigurationModel. The models are, thankfully, accompanied by detailed help_text attributes and docstrings. They're just not in the standard format.

*Reviewers*

• [ ] @mavidser

• [ ] edX Reviewer TBD