Using an umbrella application as the data connector and calling migrate/seeds on it

The idea:
I would like to have one central point/application as my DB store connector, currently, I am looking at using Postgres so let’s say I have an Ecto only application. It’s within my umbrella project. This is to allow me to easily plug new data stores (Mnesia, Riak, e.t.c) as needed for different apps in my umbrella.

The confusion/challenge
Does it make sense that my Datastore is aware of things like users, roles? I think this should be abstracted to the exact entities that handle them Auth e.t.c. If the answer is no, how do I create seeds/setup instructions from applications?