Add Docs to Setup DB, Run Migrations, and Create Models in the docs folder

[echelonnought]

Description:

Include a clear guide on how to:

• run and setup the postgres db,

• create models using sequelize orm

• run migrations on those models

Acceptance Criteria:

We should have these files in the project's docs folder with clear descriptions as to the requirements in the issue description

• DATABASE_SETUP.md

• MIGRATIONS.md

• MODELS.md