FEATURE: Delete backups based on time window (#24296)

* FEATURE: core code, tests for feature to allow backups to removed based on a time window

* FEATURE: getting tests working for time-based backup

* FEATURE: getting tests running

* FEATURE: linting

config/locales/server.en.yml

@@ -1824,6 +1824,7 @@ en:
     enable_backups: "Allow administrators to create backups of the forum"
     allow_restore: "Allow restore, which can replace ALL site data! Leave disabled unless you plan to restore a backup"
     maximum_backups: "The maximum amount of backups to keep. Older backups are automatically deleted"
+    remove_older_backups: "Remove backups older than the specified number of days. Leave blank to disable."
     automatic_backups_enabled: "Run automatic backups as defined in backup frequency"
     backup_frequency: "The number of days between backups."
     s3_backup_bucket: "The remote bucket to hold backups. WARNING: Make sure it is a private bucket."

config/site_settings.yml

@@ -2337,6 +2337,9 @@ backups:
   maximum_backups:
     client: true
     default: 5
+  remove_older_backups:
+    client: true
+    default: ""
   automatic_backups_enabled:
     default: true
   backup_frequency: