Support auditing needs by switching to has_many, through

[brettwgreen]

Switch from HABTM to has_many and has_many through:

This will allow users to add columns like id and created_at to the intermediate table and use paper_trail to track changes to this table, as well as gems like paranoia to soft-delete those records. All of this is super-important from a security auditing perspective.

Pulled code from a PR made about 9 months ago that failed tests and was abandoned. Made further changes based on my own needs to adequately support timestamp columns, soft-delete (paranoia) and paper_trail.

I am deliberately removing the records in the join table using destroy_all to trigger proper eventing with timestamps and paper_trail, and then still honoring the options removal of role records no longer in use.

[brettwgreen]

Still working through issues with callbacks... will reopen later

[khiav223577]

Looking forward to this feature!