Add migration to add default super user account

[umarkayondo]

Note: This migration references the previously created migration file in the accounts app therefore the initial migration should not be deleted. If you choose to delete it, make sure that it's recreated before this migration.

[vgkienzler]

@umarkayondo tanks a lot for this, as discussed, I suggest that we keep this for later, closer to the date when we are ready to deploy to production. This will allow us to simply delete all the migrations and the sqllight db file we we alter our models, as long the db isn't populated.