fix: Fix bugs with expanded Json-ld formats

[jimmarino]

What this PR changes/adds

Fixes issues when transforming expanded Json for contract negotiation.

Further notes

Starts to introduce expanding Json in Json-ld transformer unit tests to avoid these problems in the future. Additional PRs will resolve issues in the other Json-ld transformers as well as improve error messages.

Linked Issue(s)

Closes #2919

Checklist

• added appropriate tests?
• performed checkstyle check locally?
• added/updated copyright headers?
• documented public classes/methods?
• added/updated relevant documentation?
• assigned appropriate label? (exclude from changelog with label no-changelog)
• formatted title correctly? (take a look at the CONTRIBUTING and Etiquette for pull requests for details)

[codecov-commenter]

Codecov Report

Patch coverage: 63.63% and project coverage change: -0.39 ⚠️

Comparison is base (61669db) 66.46% compared to head (394cb11) 66.08%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2955      +/-   ##
==========================================
- Coverage   66.46%   66.08%   -0.39%     
==========================================
  Files        1036     1038       +2     
  Lines       21059    21210     +151     
  Branches     1234     1255      +21     
==========================================
+ Hits        13997    14016      +19     
- Misses       6542     6673     +131     
- Partials      520      521       +1     

Impacted Files	Coverage Δ
...tractNegotiationTerminationMessageTransformer.java	81.25% <50.00%> (+1.25%)	⬆️
...JsonObjectToContractRequestMessageTransformer.java	73.33% <60.00%> (+0.60%)	⬆️
...nld/spi/transformer/AbstractJsonLdTransformer.java	13.07% <64.00%> (ø)
...onObjectToContractAgreementMessageTransformer.java	73.07% <100.00%> (+1.37%)	⬆️

... and 1 file with indirect coverage changes

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