private MethodHandler createMethodHandler(
        final Target<?> target, final MethodMetadata md, final C requestContext) {
      if (md.isIgnored()) {
        return args -> {
          throw new IllegalStateException(md.configKey() + " is not a method handled by feign");
        };
      }

      return factory.create(target, md, requestContext);
    }
creates an api binding to the {@code target}. As this invokes reflection, care should be taken
to cache the result.
core/src/main/java/feign/ReflectiveFeign.java