Do not create setting with invalid value in data migration (#13576)

* Do not create setting with invalid value in data migration

* Add test for conf app data migration

awx/conf/tests/functional/test_migrations.py

@@ -0,0 +1,25 @@
+import pytest
+
+from awx.conf.migrations._ldap_group_type import fill_ldap_group_type_params
+from awx.conf.models import Setting
+
+from django.apps import apps
+
+
+@pytest.mark.django_db
+def test_fill_group_type_params_no_op():
+    fill_ldap_group_type_params(apps, 'dont-use-me')
+    assert Setting.objects.count() == 0
+
+
+@pytest.mark.django_db
+def test_keep_old_setting_with_default_value():
+    Setting.objects.create(key='AUTH_LDAP_GROUP_TYPE', value={'name_attr': 'cn', 'member_attr': 'member'})
+    fill_ldap_group_type_params(apps, 'dont-use-me')
+    assert Setting.objects.count() == 1
+    s = Setting.objects.first()
+    assert s.value == {'name_attr': 'cn', 'member_attr': 'member'}
+
+
+# NOTE: would be good to test the removal of attributes by migration
+# but this requires fighting with the validator and is not done here