Create database with separate script.

Creating the ATAT database requires a separate connection to one of the
default Postgres databases, like `postgres`. This updates the scripts
and secrets-tool command to handle creating the database. It also
removes database creation from Terraform and updates the documentation.

terraform/modules/postgres/main.tf

@@ -35,11 +35,3 @@ resource "azurerm_postgresql_virtual_network_rule" "sql" {
   subnet_id                            = var.subnet_id
   ignore_missing_vnet_service_endpoint = true
 }
-
-resource "azurerm_postgresql_database" "db" {
-  name                = "${var.name}-${var.environment}-atat"
-  resource_group_name = azurerm_resource_group.sql.name
-  server_name         = azurerm_postgresql_server.sql.name
-  charset             = "UTF8"
-  collation           = "en-US"
-}

terraform/modules/postgres/outputs.tf

@@ -1,3 +0,0 @@
-output "db_name" {
-  value = azurerm_postgresql_database.db.name
-}