feat: filter pages queryset more efficiently [CDD-3506]

[jrdh]

Description

Filter pages querysets more efficiently. This change adds two filter functions which can query for public and non-public pages using a single query instead of several. The queryset is also not resolved during viewset's get_queryset method.

The functions use subqueries to ensure the correct pages are filtered in and out of queries. Originally left outer joins was prefered as the best approach, however this proved incompatible with wagtail's search backend framework, whereas subqueries works.

This supersedes https://github.com/UKHSA-Internal/data-dashboard api/pull/3293 with similar performance (slightly fewer total queries):

list view including public pages:

• 165ms overall
• 35ms on queries
• 33 queries

list view including permitted non-public pages:

• 164ms overall
• 34ms on queries
• 33 queries

Fixes #CDD-3506

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Type of change

Please select the options that are relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Tech debt item (this is focused solely on addressing any relevant technical debt)

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Checklist:

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests at the right levels to prove my change is effective
• I have added screenshots or screen grabs where appropriate
• I have added docstrings in the correct style (google)

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud