* Added GraphQLTransactionTestCase
- Adds support for testing code that is executed within a transaction
Reference: https://docs.djangoproject.com/en/3.1/topics/testing/tools/#django.test.TransactionTestCase
```
For instance, you cannot test that a block of code is executing within a transaction, as is required when using select_for_update(). In those cases, you should use TransactionTestCase.
```
* Update testing.py
* Update testing.py
* Fixed formatting.
* Updated docs.
* Updated test.
* Update testing.rst
* merge master into v3
* fix order_by snake casing by checking if value is None, switch executor to execution_context_class since schema.execute no longer supports executor
* fix linting by removing duplicate defintion and test of convert_form_field_to_string_list
* Documentation missing endpoint explanation
Add some information about GRAPHQL_URL. Otherwise people run into ERROR 400 problems, if they have a different endpoint.
* Update docs/testing.rst
Co-Authored-By: Jonathan Kim <jkimbo@gmail.com>
Co-authored-by: Jonathan Kim <jkimbo@gmail.com>
