Port grants data modeling work from Django to Express API

[beechnut]

Extensive work was done on getting data modeling set up in Django. We want to leverage this by porting this work to the API backend.

We'll know we're done when:

• [x] API connects to the Postgres database
  • [x] Local
  • [x] Sandbox
• [x] API endpoint for /grants model is returning minimal grants JSON from the database
• [x] Display all grants model data for the API endpoint (no relationships, creation, editing, validation)
  • [x] Strongly-typed (types for option choices are in place)
  • [x] Verify decimal type parameters are translated correctly
• [x] Frontend app displays a few of these grants