Use a dedicated relationship model and enable dataclass support

[armanddidierjean]

Description

Please explain the changes you made here.

Checklist

• Created tests which fail without the change (if possible)
• All tests passing
• Extended the documentation, if necessary

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.55%. Comparing base (64d404b) to head (ec11183).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #606   +/-   ##
=======================================
  Coverage   81.54%   81.55%           
=======================================
  Files         128      128           
  Lines        9929     9933    +4     
=======================================
+ Hits         8097     8101    +4     
  Misses       1832     1832           

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