♻️(serializers) move dimail calls to serializers

we move all business logic from model to serializer.
all API calls (direct and from front) will keep on triggering
expected 3rd party calls while admin actions will uniquely trigger
modifications in our database.

src/backend/mailbox_manager/api/serializers.py

@@ -5,6 +5,7 @@ from rest_framework import serializers
 from core.api.serializers import UserSerializer
 
 from mailbox_manager import enums, models
+from mailbox_manager.utils.dimail import DimailAPIClient
 
 
 class MailboxSerializer(serializers.ModelSerializer):
@@ -16,6 +17,14 @@ class MailboxSerializer(serializers.ModelSerializer):
         # everything is actually read-only as we do not allow update for now
         read_only_fields = ["id"]
 
+    def create(self, validated_data):
+        """
+        Override create function to fire a request on mailbox creation.
+        """
+        client = DimailAPIClient()
+        client.send_mailbox_request(validated_data)
+        return models.Mailbox.objects.create(**validated_data)
+
 
 class MailDomainSerializer(serializers.ModelSerializer):
     """Serialize mail domain."""