fixes#5181
* application/json
* application/xml
* application/x-www-form-urlencoded
* Set requestBodyValue values to be an immutable Map, as "value". Previously stored as a normal String.
* This enables adding "errors" to the Map, for validation use
* note: getOAS3RequiredRequestBodyContentType requires state.spec,
* which is not available to state.oas3
* Add empty data param to cURL if no request body was given
Some middleware applications do not allow POST requests without a content-length header. By adding a empty data parameter to the curl command, the content-length header will be set by curl. Besides this it is more obvious to the user that no request body is sent.
* use double quotes like the rest of the curl command
* improve(getParameterSchema): ParameterSchemaDescriptor pattern
* chore: update usage of `getParameterSchema`
* consider `Parameter.content` media type when validating JSON values
