✨(models) add MailDomain status

Add some status to allow to create mailboxes only for an active domain

src/backend/mailbox_manager/enums.py

@@ -0,0 +1,15 @@
+"""
+Application enums declaration
+"""
+
+from django.db import models
+from django.utils.translation import gettext_lazy as _
+
+
+class MailDomainStatusChoices(models.TextChoices):
+    """Defines the possible statuses in which a mail domain can be."""
+
+    PENDING = "pending", _("Pending")
+    ENABLED = "enabled", _("Enabled")
+    FAILED = "failed", _("Failed")
+    DISABLED = "disabled", _("Disabled")