Add missing keywords support for OpenAPIReference (and JsonSchemaRefernece #2903

actually I went ahead and had additional discussions with both Henry Andrews (@handrews) and Darrel (@darrelmiller) (thank you both). My understanding was wrong.
Any JSON Schema keyword can appear next to $ref, some might not be applicable (not do anything) due to their nature, some might be contradictory when appearing both in the reference and the referenced schema, in which case, it's up to the application to define what the behaviour should be.

In the case where both are present, we have a precedent of returning the reference value for annotation keywords, so being consistent here makes sense. Then the application can check the reference and the target values, and compare them, if the difference is important to the application.

Any keyword in JSON schema exposed as a property in the IOpenAPISchema interface as well as in the IOpenApiSchemaMissingProperties should have:

• a corresponding setter in the JsonSchemaReference type, and serialization code to match (use x-jsonschema prefix for OAI < 3.1)
• a corresponding getter in the JsonSchemaReference type, and the deserialization code to match (use x-jsonschema prefix for OAI < 3.1)
• a corresponding setter in OpenApiSchemaReference, that maps to the reference corresponding setter
• a corresponding getter, which returns the reference value when present, otherwise the target value
• cloning and unit test code like you've started

Now, I understand this is significant work, if you want to focus on the properties you've identified first, and punt the other properties to an additional issue, let me know.

Originally posted by Vincent Biret (@baywet) in #2896 (comment)