test: add wrapper and filter tests FAN-58

[MaferMazu]

Description

This PR adds tests for the PR #5

• Add pytest and coverage to test.in and update requirements (I use python 3.8, pip 20.0.1, and pip-tools 5.3.1).
• Add support for python 3.10 in tox.
• Add backends for tests.
• Add wrappers test.
• Add pipeline module unit tests.
• Correct the test execution by creating an email_module_l_v1 backend and adding it to the plugin settings.
• Add some pylint disable comments.

How to test

• In the terminal run
  export DJANGO_SETTINGS_MODULE='nau_openedx_extensions.settings.test'
• Then, make tests
  make python-test

Notes for next steps and later improvements

• Run quality test returns an error because there are a lot of Pylint errors (If you want to test quality, you can use pylint <file-name>)
• To avoid exporting DJANGO_SETTINGS_MODULE when running unit tests and set it automatically, you need to do it in the Pytest configurations files. I can't use pytest-django because some models import Openedx platform features directly and don't have a backend in the wrappers.
• Drop support for Django 22

[felipemontoya]

@MaferMazu do you run this tests from the tutor dev bash? Or are you running the out of the containers?

[MaferMazu]

@felipemontoya I ran it out of the containers

[felipemontoya]

I think this is better to merge this sooner rather than waiting for long with the branch open