Add last modified date to TestCase and TestPlan

[veenone]

• Add updated_at field to both models with migrations.
• Show last modified date in detail view sidebars and search result tables.
• Expose updated_at via RPC API filter and update responses.
• If the entry never been modified yet, use created date on the modified date

implements #4140

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Screenshots

[atodorov]

Original approach is straight forward but will kill performance for large installations.

PR needs changes related to performance.

Please also split the changes for test case & test plan pages into 2 separate pull requests.

[atodorov]

This is a no-go!

A subquery will essentially make multiple extra queries which will have disastrous effects on performance. On a production dataset with 1684 test cases, which have 2806 historical record between all of them this results in a 2x worse performance!

We've got Kiwi TCMS installations with thousands of test cases where this query will kill the entire application.

[atodorov]

Try this instead (change what's the model we query and how we find what data to return):

1. Add

test_case_ids = TestCase.objects.filter(**query).values("id")

2. Replace TestCase.objects -> HistoricalTestCase.objects
3. The filter statement becomes .filter(id__in=test_case_ids)
4. Add history_date in the .values() argument list
5. Change the order/disctinct clause to

    .order_by("id", "-history_date")
    .distinct("id")

Which essentially means: get me the last available record of each test case which matches the query filter passed to this call and has not been removed.

Then display the "history_date" column with the title "Last modified".

[atodorov]

^^^ NOTE: the proposed approach above results in 1 extra query to fetch the relevant IDs.