Create and document an MVP DB schema using DBML

[jhodapp]

Description

This PR creates and documents an MVP DB schema for refactor_platform_rs using DBML.

GitHub Issue: Fixes #8

Changes

• Creates/documents an MVP DB schema for refactor_platform_rs using DBML
• Adds a script to automatically generate Postgresql-compatible SQL and generate a new DB within a running instance of Postgres
• Updates the users entity with new fields
• Uses autoincrement integer-based internal primary keys and external UUID-based ids

DB schema diagram generated using dbdiagram.io's export feature:

Testing Strategy

1. Drop it in a new diagram session at dbdiagram.io ensuring there are no syntactical errors
2. Run scripts/rebuild_db.sh and make sure that it creates a new refactor_platform DB in Postgres
3. Ensure you're able to log in using the refactor-platform-fe login page

Concerns

None