feat: new background work process

This removes all previous dependencies on RabbitMQ and the need to run separate cron and requeueing processes.

app/scheduled_tasks/prune_webhook_requests_scheduled_task.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class PruneWebhookRequestsScheduledTask < ApplicationScheduledTask
+
+  def call
+    Server.all.each do |s|
+      logger.info "Pruning webhook requests for server #{s.id}"
+      s.message_db.webhooks.prune
+    end
+  end
+
+  def self.next_run_after
+    quarter_to_each_hour
+  end
+
+end