feat: MPTT relations compatibility issue reproduction

[Eraldo]

Description

Trying to get an author and then the total count of the children of that author breaks when there are no children present but requested in the query.
Error:

"message": "An unknown error occurred."

The PR includes a test test_nexted_children.py, which illustrates the use case and resulting error.

FYI: Disabling the DjangoOptimizerExtension makes the test pass without any issue.

Types of Changes

• Bug reproduction for 3rd party compatibility

Summary by Sourcery

This pull request enhances the RelayAuthor model by adding MPTT relations to support hierarchical data structures. Additionally, a new test case is introduced to verify the nested children count functionality.

• Enhancements:
  • Added MPTT (Modified Preorder Tree Traversal) relation to the RelayAuthor model to support hierarchical data structures.
• Tests:
  • Introduced a new test case 'test_nested_children_total_count' to verify the nested children count functionality in the RelayAuthor model.

[sourcery-ai]

Reviewer's Guide by Sourcery

This pull request introduces an MPTT (Modified Preorder Tree Traversal) relation to the RelayAuthor model to address an issue where querying for an author and their children would break if no children were present. The changes include modifying the RelayAuthor model to inherit from MPTTModel, adding a parent field to establish the tree structure, and updating the AuthorType to include a children connection. A new test file, test_nested_children.py, is added to illustrate the issue and verify the fix.

File-Level Changes

Files	Changes
tests/relay/lazy/models.py tests/relay/lazy/a.py	Updated the RelayAuthor model to support MPTT relations and modified the AuthorType to include a children connection.
tests/relay/lazy/test_nested_children.py	Added a new test file to verify the fix for querying authors and their children.

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[sourcery-ai]

Hey @Eraldo - I've reviewed your changes and they look great!

Here's what I looked at during the review

• 🟢 General issues: all looks good
• 🟢 Security: all looks good
• 🟡 Testing: 1 issue found
• 🟢 Complexity: all looks good

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[sourcery-ai]

suggestion (testing): Missing edge case for no children

The current test only covers the case where an author has children. It would be beneficial to add a test case where an author has no children to ensure the code handles this scenario correctly.

Suggested change

	import pytest
	import pytest
	@pytest.mark.parametrize("children", [True, False])
	def test_author_children(children):
	# Your existing test code here, modified to use the 'children' parameter

[bellini666]

Closing this as #553 superseded it