Tests for hidden schemas

[Azquelt]

• Test that a field annotated with @Schema(hidden = true) is not included in the schema for the enclosing class
• Test that a resource method parameter annotated with @QueryParam and @Schema(hidden = true) creates a parameter with no schema in the openapi document
• Test that a resource method parameter annotated with @Schema(hidden = true) creates a request body with no schema in the openapi document

I wasn't hugely happy with this issue, the spec isn't clear what "hidden" means and it's hard to interpret for all the locations that the @Schema annotation could be applied. The lack of structure in the TCKs is also unhelpful in deciding how to add or structure a new set of tests.

In the end I've tested hidden = true in the scenarios listed above and required that the schema parameter is not present in the openapi document which seems reasonable, but it could also be tested in the following locations:

• Applied to a class which is used as a field in a different class
• Applied to a class which is used as a request body
• Applied to a class which is used as a request parameter
• Applied to a class which is used as a response body
• Applied to a resource method (where it would affect the response body)

Fixes #508