feat: proposed ORM model

[risharma]

This is my proposed ORM schema, can you review it? Here's the context of the ticket:

Create a small web app that allows users to sign up. Each user can optionally provide their age and their location (zip code).

After signing up, users should be able to favorite/like products and see a list of which products they liked/favorited.

Additionally, users should be able to configure account settings like whether they want to enable email notifications.

Finally, special admin users should have the ability to change a user's username or delete their account.