Create + unregister non-abstract models for tests

Prevents other test failures:
- corehq.apps.domain.tests.test_deletion_models:test_deletion_sql_models
  AssertionError: Not all Django models are covered by domain deletion.
- corehq.sql_db.tests.test_model_partitioning:TestPartitionedModelsWithMultipleDBs.test_models_are_located_in_correct_dbs('scheduling', False)
  UndefinedTable: relation "scheduling_content" does not exist

corehq/messaging/scheduling/tests/test_content.py

@@ -1,5 +1,6 @@
 from unittest.mock import Mock
 
+from django.apps import apps
 from django.test import TestCase, override_settings
 
 from corehq.apps.domain.shortcuts import create_domain
@@ -45,6 +46,18 @@ def setUpClass(cls):
         cls.sms_translations.set_translations('es', {})
         cls.sms_translations.save()
 
+        global Content, Schedule
+
+        class Content(AbstractContent):
+            pass
+
+        class Schedule(AbstractSchedule):
+            pass
+
+        # unregister test models to prevent other test failures
+        del apps.get_app_config("scheduling").models["content"]
+        del apps.get_app_config("scheduling").models["schedule"]
+
     @classmethod
     def tearDownClass(cls):
         cls.sms_translations.delete()
@@ -210,11 +223,3 @@ def test_sms_language_fallback(self):
             content.get_translation_from_message_dict(self.domain_obj, message_dict, user_lang),
             message_dict['*']
         )
-
-
-class Content(AbstractContent):
-    pass
-
-
-class Schedule(AbstractSchedule):
-    pass

corehq/messaging/scheduling/tests/test_recipients.py

@@ -2,6 +2,7 @@
 import uuid
 from datetime import time
 
+from django.apps import apps
 from django.test import TestCase, override_settings
 
 from unittest.mock import patch
@@ -128,6 +129,14 @@ def setUpClass(cls):
         cls.process_pillow_changes = process_pillow_changes('DefaultChangeFeedPillow')
         cls.process_pillow_changes.add_pillow(get_case_messaging_sync_pillow())
 
+        global ScheduleInstance
+
+        class ScheduleInstance(AbstractScheduleInstance):
+            pass
+
+        # unregister test model to prevent other test failures
+        del apps.get_app_config("scheduling").models["scheduleinstance"]
+
     @classmethod
     def tearDownClass(cls):
         cls.domain_obj.delete()
@@ -844,7 +853,3 @@ def test_phone_number_preference(self):
         self.assertPhoneEntryCount(3)
         self.assertPhoneEntryCount(1, only_count_two_way=True)
         self.assertTwoWayEntry(Content.get_two_way_entry_or_phone_number(user), '23456')
-
-
-class ScheduleInstance(AbstractScheduleInstance):
-    pass