Replace AbstractMongoTest with JUnit Externalresource

I went to use test. AbstractMongoTest and realized that it was broken and nothing actually used it anyway. So I would like to replace it with a JUnit ExternalResource.

I also noticed that there are several versions of AbstractMongoTest in different places that are not all the same. If this change is accepted, I will make a story to replace all the copy/paste versions with the new ExternalResource.
Want to add an example dummy unit test that actually uses this resource to make sure it works?  Maybe just verify can interact with the server and do some basic stuff like create a doc and verify it got created.