v2.0 - Hasura 2.0+ Release

Updates / New Features

• Updated to use Hasura 2.0+ and Hasura Metadata v3
  • Makes more effective use of Actions for mapping Django REST endpoints to GraphQL nodes (no REST usage).
• Added healthchecks to docker-compose (to help with the order-of-operations of installing migrations Postgres Up > Django Migrations > Hasura Migrations)
• Added DJANGO_DEFAULT_USERNAME, DJANGO_DEFAULT_PASSWORD, DJANGO_DEFAULT_EMAIL, DJANGO_DEFAULT_ROLE in env vars (to create initial superuser).