♻️(tests) refacto dimail tests with fixtures

test_api_mailboxes_create exceeded 1000 lines. By using fixtures, we can
at least factorize dimail response when token is ok or mailbox_data sent
to our API when creating a mailbox.

src/backend/mailbox_manager/api/client/serializers.py

@@ -3,6 +3,7 @@
 from logging import getLogger
 
 from django.contrib.auth.hashers import make_password
+from django.core import exceptions as django_exceptions
 
 from requests.exceptions import HTTPError
 from rest_framework import exceptions, serializers
@@ -44,10 +45,17 @@ class MailboxSerializer(serializers.ModelSerializer):
                 "password": make_password(None),  # generate an unusable password
             }
         )
-        if mailbox.domain.status == enums.MailDomainStatusChoices.ENABLED:
-            client = DimailAPIClient()
+
+        if validated_data["domain"].status == enums.MailDomainStatusChoices.ENABLED:
             # send new mailbox request to dimail
-            response = client.create_mailbox(mailbox, self.context["request"].user.sub)
+            client = DimailAPIClient()
+            try:
+                response = client.create_mailbox(
+                    mailbox, self.context["request"].user.sub
+                )
+            except django_exceptions.ValidationError as exc:
+                mailbox.delete()
+                raise exc
 
             mailbox.status = enums.MailDomainStatusChoices.ENABLED
             mailbox_data = response.json()
@@ -68,7 +76,6 @@ class MailboxSerializer(serializers.ModelSerializer):
                     mailbox,
                 )
 
-        # actually save mailbox on our database
         return mailbox