django_dumpdata, django_loaddata: new modules (#10726)

* django module, module_utils: adjustments

* more fixes

* more fixes

* further simplification

* django_dumpdata/django_loaddata: new modules

* Update plugins/modules/django_dumpdata.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* add note about idempotency

---------

Co-authored-by: Felix Fontein <felix@fontein.de>

tests/unit/plugins/modules/test_django_loaddata.py

@@ -0,0 +1,13 @@
+# Copyright (c) Alexei Znamensky (russoz@gmail.com)
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+
+from ansible_collections.community.general.plugins.modules import django_loaddata
+from .uthelper import UTHelper, RunCommandMock
+
+
+UTHelper.from_module(django_loaddata, __name__, mocks=[RunCommandMock])