Re-allocate IP address when retrying deliveries to prevent stuck messages when config changes

app/jobs/unqueue_message_job.rb

@@ -257,6 +257,8 @@ class UnqueueMessageJob < Postal::Job
                 if result.retry
                   log "#{log_prefix} Message requeued for trying later."
                   queued_message.retry_later(result.retry.is_a?(Fixnum) ? result.retry : nil)
+                  queued_message.allocate_ip_address
+                  queued_message.update_column(:ip_address_id, queued_message.ip_address&.id)
                 else
                   log "#{log_prefix} Message processing completed."
                   queued_message.message.endpoint.mark_as_used