Refactor #888

Updated by bmbouter over 6 years ago

After pulp-manage-db performs all the migrations it should load all the models for the core collections (repos, tasks, repo_content_units, etc.) and run the ensure_indexes() method on the models to make sure that the Pulp required indexes are maintained.

* Create a list that stores the class paths to provide the loading of all models for core collections
* Updates to pulp-manage-db to call out platform models by class to ensure the indexes are created
"Platform models that have already been converted": are included in the list of models above
* Updates to pulp-manage-db calls ensure_indexes() on each loaded class in the list above
called out
* Mongoengine conversion guide is updated to include adding the model to this collection of calls.