fix: add nested catalog test + types registration

[wolf4ood]

What this PR changes/adds

Fixes JSON serde for Catalog when datasets contains an embedded catalog by
registering Catalog and Dataset types in the TypeManager where now Dataset is polymorphic eclipse-edc/Connector#4362

Why it does that

bugfix

Further notes

List other areas of code that have changed but are not necessarily linked to the main feature. This could be method
signature changes, package declarations, bugs that were encountered and were fixed inline, etc.

Linked Issue(s)

Closes # <-- insert Issue number if one exists

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.55%. Comparing base (2d71ca0) to head (e5018cf).
Report is 66 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #224      +/-   ##
==========================================
+ Coverage   65.43%   73.55%   +8.11%     
==========================================
  Files          25       25              
  Lines         434      571     +137     
  Branches       15       25      +10     
==========================================
+ Hits          284      420     +136     
+ Misses        135      132       -3     
- Partials       15       19       +4     

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