set catalog flavour from book

[elfkuzco]

Changes

• set catalog flavour from book instead of zim metadata since book flavours can now be updated (see view books and update book flavour #299)

This fixes #306

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.60%. Comparing base (4f0bf5f) to head (f7f9100).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #307   +/-   ##
=======================================
  Coverage   81.60%   81.60%           
=======================================
  Files          58       58           
  Lines        2604     2604           
  Branches      264      264           
=======================================
  Hits         2125     2125           
  Misses        407      407           
  Partials       72       72           

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[benoit74]

LGTM