Upgrade decidim to 0.28

[fblupi]

Fixes #54

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.38%. Comparing base (072d60a) to head (fe06e70).

❗ Current head fe06e70 differs from pull request most recent head 8444882. Consider uploading reports for the commit 8444882 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #55      +/-   ##
==========================================
+ Coverage   98.39%   99.38%   +0.99%     
==========================================
  Files          52       51       -1     
  Lines         994      973      -21     
==========================================
- Hits          978      967      -11     
+ Misses         16        6      -10     

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[davidbeig]

Perfect!

Thanks for fixing the CI problems and the tests.

Great work!