Serializza gli invii SMTP su una coda unica per non far chiudere Aruba.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/jobs/drain_outbound_job.rb

@@ -0,0 +1,16 @@
+class DrainOutboundJob < ApplicationJob
+  queue_as :mailers
+
+  def perform
+    result = Mailings::OutboundQueue.drain_one!
+    return unless result.in?(%i[sent deferred wait])
+    return unless Mailings::OutboundQueue.queued_scope.exists?
+
+    wait = Mailings::OutboundQueue.seconds_until_next_slot
+    wait = 0 if wait.blank? || wait.negative?
+    max_wait = [ Mailings::OutboundQueue.min_interval.to_f, 2.minutes ].max + 5.seconds
+    return if wait > max_wait
+
+    self.class.set(wait: wait).perform_later
+  end
+end