👔(dimail) allow creation of "pending" mailboxes

Previously, mailbox creation was restricted to "enabled" domains.
We now allow users to create mailboxes on pending and failed domains.
Mailboxes thus created have the "pending" mailboxes status.

src/backend/mailbox_manager/migrations/0014_mailbox_status.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.1.3 on 2024-11-18 14:45
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('mailbox_manager', '0013_remove_maildomain_secret'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='mailbox',
+            name='status',
+            field=models.CharField(choices=[('pending', 'Pending'), ('enabled', 'Enabled'), ('failed', 'Failed'), ('disabled', 'Disabled')], default='pending', max_length=20),
+        ),
+    ]