pgbackrest: automate "backup-standby" setup

Implemented an automatic addition of standby servers to the stanza configuration.

This feature is triggered when the `backup-standby` option is set to `y` in `pgbackrest_conf`.
Standby servers are added sequentially, starting from `pg2-host`, `pg3-host`, and so on.

roles/pgbackrest/templates/pgbackrest.conf.j2

@@ -7,4 +7,14 @@
 {% for stanza in pgbackrest_conf.stanza %}
 {{ stanza.option }}={{ stanza.value }}
 {% endfor %}
-
+{% if any(item.option == "backup-standby" and item.value == "y" for item in pgbackrest_conf.global) %}
+{% set host_index = 2 %}
+{% for host in groups['postgres_cluster'] %}
+  {% if host != ansible_hostname %}
+    pg{{ host_index }}-host={{ host }}
+    pg{{ host_index }}-port={{ postgresql_port }}
+    pg{{ host_index }}-path={{ postgresql_data_dir }}
+    {% set host_index = host_index + 1 %}
+  {% endif %}
+{% endfor %}
+{% endif %}

vars/main.yml

@@ -508,6 +508,7 @@ pgbackrest_conf:
     - { option: "archive-async", value: "y" } # Enables asynchronous WAL archiving (details: https://pgbackrest.org/user-guide.html#async-archiving)
     - { option: "archive-get-queue-max", value: "1GiB" }
 #    - { option: "archive-push-queue-max", value: "100GiB" }
+    - { option: "backup-standby", value: "y" } # When set to 'y', standby servers will be automatically added to the stanza section.
 #    - { option: "", value: "" }
   stanza:  # [stanza_name] section
     - { option: "pg1-path", value: "{{ postgresql_data_dir }}" }