refactor: remove all legacy directus environment variables and standardize on postgres

docker-compose.yaml

@@ -89,9 +89,9 @@ services:
     env_file:
       - ${ENV_FILE:-.env}
     environment:
-      POSTGRES_DB: ${DIRECTUS_DB_NAME:-directus}
-      POSTGRES_USER: ${DIRECTUS_DB_USER:-directus}
-      POSTGRES_PASSWORD: ${DIRECTUS_DB_PASSWORD:-directus}
+      POSTGRES_DB: ${POSTGRES_DB:-payload}
+      POSTGRES_USER: ${POSTGRES_USER:-postgres}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-postgres}
     volumes:
       - mb-grid-db-data:/var/lib/postgresql/data