Add Terraform modules for creating databases

[pacphi]

Some charts have dependencies on MySQL or Postgres.

Consider delegating to pre-configured modules in Terraform docs or registry, like:

• AWS

  • https://www.terraform.io/docs/providers/aws/r/rds_cluster_instance.html
  • https://registry.terraform.io/modules/terraform-aws-modules/rds-aurora/aws/2.19.0

• Azure

  • https://www.terraform.io/docs/providers/azurerm/r/mysql_database.html
  • https://www.terraform.io/docs/providers/azurerm/r/postgresql_database.html

• Google

  • https://registry.terraform.io/modules/GoogleCloudPlatform/sql-db/google/3.2.0
  • https://www.terraform.io/docs/providers/google/r/sql_database_instance.html

[pacphi]

As of 54eb93f we now have support for creating MySQL and PostgreSQL instances on GCP.