service: Allow custom postgres image

roles/service/defaults/main.yaml

@@ -11,6 +11,7 @@ service_container_secrets: []
 service_container_env: {}
 
 service_database_type: none
+service_postgres_image: docker.io/library/postgres
 service_redis: false
 
 service_additional_containers: []

roles/service/meta/argument_specs.yaml

@@ -182,11 +182,17 @@ argument_specs:
           - postgres
           - none
         default: none
+      service_postgres_image:
+        description: Postgresql image to use.
+        type: str
+        required: false
+        default: docker.io/library/postgres
       service_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.
           - Required if service_database_type is postgres, does nothing otherwise
+          - If a custom postgres image is specified, see that image documentation for supported tags.
         type: str
         required: false
       service_redis:

roles/service/tasks/database.yaml

@@ -4,7 +4,7 @@
     name: container
   vars:
     container_name: "{{ service_name }}-{{ service_database_type }}" # This doesn't use _service_database_name to allow container role handlers to work
-    container_image: "docker.io/library/postgres:{{ service_postgres_tag }}"
+    container_image: "{{ service_postgres_image }}:{{ service_postgres_tag }}"
     container_mounts:
       - type: volume
         source: "{{ _service_database_name }}"