protected <E extends Annotation> void registerClassAnnotation(
      Class<E> annotationType, DeclarativeContract.AnnotationProcessor<E> processor) {
    registerClassAnnotation(
        annotation -> annotation.annotationType().equals(annotationType), processor);
  }
Called while class annotations are being processed

@param annotationType to be processed
@param processor function that defines the annotations modifies {@link MethodMetadata}
core/src/main/java/feign/DeclarativeContract.java