🚨(linter) add missing docstrings

Title says all there is to say…

src/backend/mailbox_manager/api/__init__.py

@@ -0,0 +1 @@
+"""Mailbox manager API module."""

src/backend/mailbox_manager/api/permissions.py

@@ -18,6 +18,7 @@ class MailBoxPermission(core_permissions.IsAuthenticated):
     """Permission class to manage mailboxes for a mail domain"""
 
     def has_permission(self, request, view):
+        """Check permission based on domain."""
         domain = models.MailDomain.objects.get(slug=view.kwargs.get("domain_slug", ""))
         abilities = domain.get_abilities(request.user)
         return abilities.get(request.method.lower(), False)

src/backend/mailbox_manager/api/viewsets.py

@@ -40,6 +40,7 @@ class MailDomainViewSet(
     queryset = models.MailDomain.objects.all()
 
     def get_queryset(self):
+        """Restrict results to the current user's team."""
         return self.queryset.filter(accesses__user=self.request.user)
 
     def perform_create(self, serializer):
@@ -100,6 +101,7 @@ class MailDomainAccessViewSet(
     detail_serializer_class = serializers.MailDomainAccessSerializer
 
     def get_serializer_class(self):
+        """Chooses list or detail serializer according to the action."""
         if self.action in {"list", "retrieve"}:
             return self.list_serializer_class
         return self.detail_serializer_class