✨(dimail) send pending mailboxes upon domain activation

send creation requests to dimail for all pending mailboxes
when domain goes from "pending" to "enabled".

src/backend/mailbox_manager/migrations/0016_alter_mailbox_domain.py

@@ -0,0 +1,19 @@
+# Generated by Django 5.1.5 on 2025-01-31 17:44
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('mailbox_manager', '0015_change_mailboxes_status_to_enabled'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='mailbox',
+            name='domain',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='mailboxes', to='mailbox_manager.maildomain'),
+        ),
+    ]