Add method to create admin user and developer application with the required AbandonAuth Callback URI on first startup

[fisher60]

Summary

Currently the application is first deployed in a broken state that requires the user to dig into the database and create a User, DeveloperApplication, and CallbackUri very manually. This should not be necessary and it should be much easier to do a first-time launch of the application.

As of writing this, we do not yet have username + password auth for local testing, that will be completed in #54
So we may need the ability for a user login another way or perhaps provide their discord user ID for first-time startups.

It may be good to complete this alongside #54

Acceptance Criteria

A method exists that allows a user to be created with a developer application and the required callback URI for the AbandonAuth UI login. Ideally the creation of the ID for the developer application is deterministic or can be specified so that it can be set as a default value in the sample.env file.