promote book with empty actions if possible

[elfkuzco]

Changes

• remove restriction to reject promotion when there are no actions to perform
• show button to promote book in UI when there are no actions to perform

This closes #429

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.69%. Comparing base (19356da) to head (1b12b51).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #434      +/-   ##
==========================================
- Coverage   80.70%   80.69%   -0.02%     
==========================================
  Files          64       64              
  Lines        3705     3703       -2     
  Branches      438      437       -1     
==========================================
- Hits         2990     2988       -2     
  Misses        576      576              
  Partials      139      139              

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[benoit74]

LGTM