fix messaging bus

lib/policy_service/message_bus.ex

@@ -1,11 +1,11 @@
 defmodule PolicyService.MessageBus do
   use AMQP
 
-  def publish(routing_key, event) do
+  def publish(exchange, routing_key, event) do
     payload = Jason.encode!(event)
 
     :ok =
-      AMQP.Basic.publish(channel(), "policy_service.events", routing_key, payload,
+      AMQP.Basic.publish(channel(), exchange, routing_key, payload,
         content_type: "application/json",
         persistent: true
       )
@@ -18,4 +18,4 @@ defmodule PolicyService.MessageBus do
   end
 
   defp amqp_url, do: Application.fetch_env!(:policy_service, :amqp_url)
-end
+end