Resource Object Uniqueness is Not Enforced

[DQSevilla]

Describe the bug The uniqueness of resource objects (using type+id pairs) is not being enforced by Marshal or Unmarshal

Expected behavior An error should be produced whenever two resource objects or resource linkages are referenced in a document, which have the same type+id pair.

Links https://go.dev/play/p/UoFxKltVVI4

Additional context N/A