[JAVA] type=string format=byte not serialised correctly in header

[UKreher]

Description

I have a byte[] (type=string format=byte) as header parameter. For creating (the header of) the request for calling the operation ApiClient.parameterToString(Object) will be used. While this uses JSON for handling date types, it uses Object.toString() for all other types including byte[]. With the changes of #4824 the byte[] should be serialised properly when delegating to JSON instead of calling Object.toString().

Swagger-codegen version

swagger-codegen-cli-3.0.8

Swagger declaration file content or url

Command line used for generation

Steps to reproduce

Related issues/PRs

#4824

Suggest a fix/enhancement

Apply the special treatment of byte[] introduced with #4824 also to ApiClient.parameterToString(Object). And fix this in all relevant files of the template ApiClient.mustache (see #9411).