This is in record and not mongo-record, so having any Mongo code here, obviously doesn't make sense.

However, creating a `ConnectionIdentifier` to use with Record would be a good idea. 

There already is one in the db package, but that's all SQL db code and I don't want record to depend on the db package.

We could move `ConnectionIdentifier` to the common package and make the appropriate deprecations. I'd also have to deprecate `MongoIdentifier`.