feat: use extended images as default for Database Lab, instead of official images for Postgres(custom-images#1)

Author: agneum

configs/config.sample.yml

@@ -42,13 +42,13 @@ provision:
 
     # Database Lab provisions thin clones using Docker containers, we need
     # to specify which Postgres Docker image is to be used when cloning.
-    # The default is the official Postgres image
-    # (See https://hub.docker.com/_/postgres).
-    # Any custom Docker image that runs Postgres with PGDATA located
+    # The default is the extended Postgres image built on top of the official Postgres image
+    # (See https://hub.docker.com/repository/docker/postgresai/extended-postgres).
+    # Any custom or official Docker image that runs Postgres with PGDATA located
     # in "/var/lib/postgresql/pgdata" directory. Our Dockerfile
     # (See https://gitlab.com/postgres-ai/database-lab/snippets/1932037)
     # is recommended in case if customization is needed.
-    dockerImage: "postgres:12-alpine"
+    dockerImage: "postgresai/extended-postgres:12"
 
     # Use sudo for ZFS/LVM and Docker commands if Database Lab server running
     # outside a container.