Fix duplicate community library submission

[AlexVelezLl]

Summary

Fixes community library submission ordering when requesting the latest submission. The error occurred because on the submission side panel, we query the latest submission to know if a submission already exists, but the ordering was set to "-updated_date" by default. Therefore, if a previous submission was recently updated, we will get this previous submission, instead of the "newer created submission". Therefore, allowing the user to make the request to create a submission that already exists.

References

Closes #5766.

Reviewer guidance

• Create two submissions S1 for version v1, S2 for version v2 for a given channel.
• Aprove S1.
• Without publishing any new versions, go to the submission side panel. You should see that a submission for v2 already exists, and shouldn't allow creating a new submission.

[rtibblesbot]

Clean fix for the duplicate submission bug.

CI pending (frontend tests, Python unit tests, linting still running). No UI files changed.

• praise: Root cause is well-identified — the hardcoded -date_updated ordering caused recently-updated older submissions to shadow newer ones, allowing duplicate creation. The fix correctly separates the default ordering from the queryset and enables client-specified ordering via ValuesViewsetOrderingFilter, which is the established pattern in this codebase.

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@rtibblesbot's comments are generated by an LLM, and should be evaluated accordingly

How was this generated?

Reviewed the pull request diff checking for:

• Correctness: bugs, edge cases, undocumented behavior, resource leaks, hardcoded values
• Design: unnecessary complexity, naming, readability, comment accuracy, redundant state
• Architecture: duplicated concerns, minimal interfaces, composition over inheritance
• Testing: behavior-based assertions, mocks only at hard boundaries, accurate coverage
• Completeness: missing dependencies, unupdated usages, i18n, accessibility, security
• Principles: DRY (same reason to change), SRP, Rule of Three (no premature abstraction)
• Checked CI status and linked issue acceptance criteria
• For UI changes: inspected screenshots for layout, visual completeness, and consistency

[rtibblesbot]

praise: Good design — setting ordering = "-date_updated" as the viewset default preserves backward compatibility for all other callers while enabling the frontend to override with -date_created when needed.

[marcellamaki]

thank you @AlexVelezLl ! @pcenov, although I am approving and merging, I am tagging this as "needs QA" for testing on unstable (using the reviewer guidance above)