✨(aliases) warn that domain is out of sync when unexpected 404

deleting an alias should trigger a request to dimail. if dimail's
response if a 404, it means people and dimail are out of sync with
each other. log error and warn user

src/backend/mailbox_manager/tests/api/aliases/test_api_aliases_delete.py

@@ -2,6 +2,7 @@
 Tests for aliases API endpoint in People's app mailbox_manager.
 Focus on "list" action.
 """
+# pylint: disable=W0613
 
 import re
 
@@ -67,7 +68,8 @@ def test_api_aliases_delete__viewer_forbidden():
     assert models.Alias.objects.count() == 1
 
 
-def test_api_aliases_delete__viewer_can_delete_self_alias():
+@responses.activate
+def test_api_aliases_delete__viewer_can_delete_self_alias(dimail_token_ok):
     """
     Authenticated users should be allowed to delete aliases when linking
     to their own mailbox.
@@ -80,30 +82,8 @@ def test_api_aliases_delete__viewer_can_delete_self_alias():
         domain=mail_domain, destination=authenticated_user.email
     )
 
-    client = APIClient()
-    client.force_login(authenticated_user)
-    response = client.delete(
-        f"/api/v1.0/mail-domains/{mail_domain.slug}/aliases/{alias.local_part}/",
-    )
-
-    assert response.status_code == status.HTTP_204_NO_CONTENT
-    assert not models.Alias.objects.exists()
-
-
-@responses.activate
-def test_api_aliases_delete__administrators_allowed():
-    """
-    Administrators of a mail domain should be allowed to delete accesses excepted owner accesses.
-    """
-    authenticated_user = core_factories.UserFactory()
-    mail_domain = factories.MailDomainFactory(
-        users=[(authenticated_user, enums.MailDomainRoleChoices.ADMIN)]
-    )
-    alias = factories.AliasFactory(domain=mail_domain)
-
     # Mock dimail response
-    responses.add(
-        responses.POST,
+    responses.delete(
         re.compile(r".*/aliases/"),
         status=status.HTTP_204_NO_CONTENT,
         content_type="application/json",
@@ -117,3 +97,63 @@ def test_api_aliases_delete__administrators_allowed():
 
     assert response.status_code == status.HTTP_204_NO_CONTENT
     assert not models.Alias.objects.exists()
+
+
+@responses.activate
+def test_api_aliases_delete__administrators_allowed(dimail_token_ok):
+    """
+    Administrators of a mail domain should be allowed to delete accesses excepted owner accesses.
+    """
+    authenticated_user = core_factories.UserFactory()
+    mail_domain = factories.MailDomainFactory(
+        users=[(authenticated_user, enums.MailDomainRoleChoices.ADMIN)]
+    )
+    alias = factories.AliasFactory(domain=mail_domain)
+
+    # Mock dimail response
+    responses.delete(
+        re.compile(r".*/aliases/"),
+        status=status.HTTP_204_NO_CONTENT,
+        content_type="application/json",
+    )
+
+    client = APIClient()
+    client.force_login(authenticated_user)
+    response = client.delete(
+        f"/api/v1.0/mail-domains/{mail_domain.slug}/aliases/{alias.local_part}/",
+    )
+
+    assert response.status_code == status.HTTP_204_NO_CONTENT
+    assert not models.Alias.objects.exists()
+
+
+@responses.activate
+def test_api_aliases_delete__404_out_of_sync(dimail_token_ok):
+    """
+    Should return a clear message when dimail returns 404 not found.
+    """
+    authenticated_user = core_factories.UserFactory()
+    mail_domain = factories.MailDomainFactory(
+        users=[(authenticated_user, enums.MailDomainRoleChoices.ADMIN)]
+    )
+    alias = factories.AliasFactory(domain=mail_domain)
+
+    # Mock dimail response
+    responses.delete(
+        re.compile(r".*/aliases/"),
+        json={"detail": "Not found"},
+        status=status.HTTP_404_NOT_FOUND,
+        content_type="application/json",
+    )
+
+    client = APIClient()
+    client.force_login(authenticated_user)
+    response = client.delete(
+        f"/api/v1.0/mail-domains/{mail_domain.slug}/aliases/{alias.local_part}/",
+    )
+    assert response.status_code == status.HTTP_200_OK
+    assert (
+        response.json()
+        == "Alias already deleted. Domain out of sync, please contact our support."
+    )
+    assert not models.Alias.objects.exists()