Added @IgnoreParameter meta annotation

[nightfire2]

This is an attempt to add the custom parameter annotations ability requested #2890 in a way that is not intrusive to the existing Retrofit API surface.

I added an @IgnoreParameter meta annotation that can be applied to any custom parameter annotation that then causes Retrofit to ignore it during processing. The developer is then free to handle the annotation in a custom request interceptor if they so choose.

This approach preserves the behavior of any existing non Retrofit managed parameters causing Retrofit to throw an exception when building the client.

Example Usage

@IgnoreParameter
@Target(PARAMETER)
@Retention(RUNTIME)
public @interface CustomParam { }

public interface ExampleClient {
   @GET
   Call<Object> test(@CustomParam String myParam);
}

The biggest downside to this method is that it requires just-in-time handling of any custom annotations in your interceptor which is not ideal but not worse than being unable to do it in the first place in my opinion.

I'm also not satisfied with the name. @IgnoreParameter seems a little clunky so I'm open to suggestions.