feat: add negotiation endpoint api spec examples

[ndr-brt]

What this PR changes/adds

Add negotiation endpoint api spec examples

Why it does that

documentation

Further notes

• remove unneeded Dtos and simplified the object hierarchy without changing the api
• deprecated 2 api fields as they are not used anymore
• had to introduce a ManagementApiTypeRegistry that's like a wrapper around the TypeTransferRegistry, the first will use the transformers registered on itself and, if not found will rely on the latter (called fallback). This was to permit the co-existance of two ContractNegotiation to JsonObject transformers.
• created transfer-core extension that superseded dsp-transform (as described in extract a transform-core module #2883)
• type transformation has been tied to the ApiConfiguration, because the transformation is something related to the api, needed to map from the serialized data to the domain model one, and every api context could have its own transformation. With this PR we'll have the dsp context use the standard TypeTransformerRegistry and the management using the mentioned ManagementApiTypeRegistry, because every context could have a different way of serializing/deserializing domain objects. I guess in the future this could evolve in having also a dsp transformer registry.

Linked Issue(s)

Closes #3146
Closes #2883

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[codecov-commenter]

Codecov Report

Patch coverage: 70.22% and project coverage change: +6.29 🎉

Comparison is base (c3b245f) 65.90% compared to head (434735e) 72.20%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3283      +/-   ##
==========================================
+ Coverage   65.90%   72.20%   +6.29%     
==========================================
  Files         836      837       +1     
  Lines       16849    16867      +18     
  Branches      934      951      +17     
==========================================
+ Hits        11105    12178    +1073     
+ Misses       5379     4296    -1083     
- Partials      365      393      +28     

Impacted Files	Coverage Δ
...ipse/edc/connector/core/CoreServicesExtension.java	94.44% <ø> (ø)
...pse/edc/junit/assertions/AbstractResultAssert.java	63.63% <0.00%> (ø)
...pse/edc/core/transform/TransformerContextImpl.java	86.66% <ø> (ø)
...dc/core/transform/TypeTransformerRegistryImpl.java	100.00% <ø> (ø)
...transform/transformer/OdrlTransformersFactory.java	0.00% <ø> (ø)
...ansformer/from/JsonObjectFromAssetTransformer.java	94.11% <ø> (ø)
...sformer/from/JsonObjectFromCatalogTransformer.java	100.00% <ø> (ø)
...ormer/from/JsonObjectFromCriterionTransformer.java	90.90% <ø> (ø)
...mer/from/JsonObjectFromDataServiceTransformer.java	81.81% <ø> (ø)
...sformer/from/JsonObjectFromDatasetTransformer.java	100.00% <ø> (ø)
... and 45 more

... and 59 files with indirect coverage changes

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[paullatzelsperger]

approving based on PR description