service: Make postgres version configurable

roles/service/meta/argument_specs.yml

@@ -54,6 +54,11 @@ argument_specs:
           set a password for the mariadb root user
         type: dict
         required: false
+      docker_postgres_tag:
+        description: 'Postgresql version to use. Can be debian (n) or alpine-based (n-alpine), where n can be major version like 14 or minor like 14.13.'
+        type: str
+        required: false
+        default: 14-alpine
       docker_mariadb_config:
         description: |
           A dict specifying config for mariadb. For example