Add unused app with manytomany field

tests/test_project/app_add_manytomany_field/models.py

@@ -0,0 +1,9 @@
+from django.db import models
+
+
+class A(models.Model):
+    pass
+
+
+class B(models.Model):
+    many_to_many = models.ManyToManyField(A)