docs: private static boolean isReturnTypeDecodable(HttpResponseDecodeData decodeData) {
          Type returnType = decodeData.returnType();
          if (returnType == null) {
              return false;
          } else {
              return !FluxUtil.isFluxByteBuf(returnType)
                      && !(TypeUtil.isTypeOrSubTypeOf(returnType, Mono.class) && TypeUtil.isTypeOrSubTypeOf(TypeUtil.getTypeArgument(returnType), Void.class))
                      && !TypeUtil.isTypeOrSubTypeOf(returnType, byte[].class)
                      && !TypeUtil.isTypeOrSubTypeOf(returnType, Void.TYPE) && !TypeUtil.isTypeOrSubTypeOf(returnType, Void.class);
          }
      }