Adapt custom fields for the 0.28

[microstudi]

• Config UI
• Builder
• Form Presenter
• Proposal presenter (dt/dd)
• TipTap (richtext) plugin
• Disable sortable
• Custom fields in lang tabs
• loading-spinner => contianer-spinner
• Allow to customize CDN for anguages
• proposal wizard
• collaborative draft
• Disable amendment post-processing for body
• Tests

fixes #217

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.46%. Comparing base (a851688) to head (81a9f3f).
Report is 40 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #277      +/-   ##
===========================================
- Coverage    96.02%   93.46%   -2.56%     
===========================================
  Files           97      125      +28     
  Lines         2440     3521    +1081     
===========================================
+ Hits          2343     3291     +948     
- Misses          97      230     +133     

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