feat: automatic replication mode for garage

roles/garage/defaults/main.yml

@@ -2,5 +2,3 @@
 
 garage_version: v0.8.1
 garage_arch: x86_64
-
-garage_replication_mode: 1

roles/garage/tasks/main.yml

@@ -20,5 +20,8 @@
   template:
     src: garage.toml.j2
     dest: /etc/garage.toml
+  vars:
+    cluster_group: "{{ group_names | map('regex_search', '.+_cluster') | select('string') | first }}"
+    garage_replication_mode: "{{ groups[cluster_group] | length if (groups[cluster_group]|length) <=3 else 3 }}"
   notify:
     - restart garage