Make Hasura work with Heroku for CI/CD and DevOps

This is an attempt to make Hasura work with Heroku for automatically migrating new changes pushed to Master onto a staging server in Heroku.

More info of Hasura's automatic migrations and metadata: https://hasura.io/docs/1.0/graphql/manual/migrations/advanced/auto-apply-migrations.html#applying-migrations

I found solutions to some of the problems I found while trying to do this here: hasura/graphql-engine#4651

Also thanks for sander on Discord for helping me out!

It works on heroku with this custom image

Important things to set in the Heroku server

Make sure to set in Heroku's Config Vars:

1. HASURA_GRAPHQL_DATABASE_URL to the same value in DATABASE_URL
2. HASURA_GRAPHQL_CLI_ENVIRONMENT to default

Might need to restart the Dynos with More > Restart all Dynos

One click deploy