query db for latest books during zim URL computation

[elfkuzco]

Rationale

This PR refactors the way zim URLs are computed by using a subquery to get the books which are the latest per title/flavor combination. It then joins this subquery to the original query and building up a column is_latest if the current book date matches the one from the latest subquery. This way, we can/cannot have a view URL depending on if the latest book is included in the book IDs to compute their URL.

Changes

• build up the list of titles for all the book IDs given
• use subquery to get the latest books for the titles
• join original query to the subquery since all the books will always have one title_id/flavor. This is necessary to build up the is_latest property
• sort books by zim metadata Date first before created_at. This will fix the issue in Computation of ZIM to view has a bug when title changed #253

This fixes #253
This fixes #254

[codecov]

Codecov Report

❌ Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.38%. Comparing base (b78d74a) to head (aca6d90).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
backend/src/cms_backend/db/books.py	81.81%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #262      +/-   ##
==========================================
- Coverage   81.41%   81.38%   -0.04%     
==========================================
  Files          53       53              
  Lines        2228     2235       +7     
  Branches      216      218       +2     
==========================================
+ Hits         1814     1819       +5     
  Misses        357      357              
- Partials       57       59       +2     

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