AddRequestParameter double encodes parameter value

[onacit]

Describe the bug
AddRequestParameter encodes the already-encoded value when other parameter is encoded.

There is an remote endpoint which has two request parameters(Say, a and b) which each may need to be url-encoded.

Within my route, I'm intending putting the b parameter's value.

Per, #2717, I configured the b parameter's value as url-encoded.

When sending a with an ascii value, it works.

When sending a with an url-encoded value, the b parameter's value is double-encoded.

# application.yaml

spring:
  cloud:
    gateway:
      routes:
        filters:
          - AddRequestParameter=b, %2F

CLIENT                  GATEWAY
--------------------------------------------------
a=%2F                   a=%2F&b=%2F   OK
a=a                     a=a&b=%252F   NOT OK

[onacit]

Here comes what I've used to solve my case.

            @Override
            public Mono<Void> filter(final ServerWebExchange exchange, final GatewayFilterChain chain) {
                final var request = exchange.getRequest();
                final var uri = request.getURI();
                final var builder = UriComponentsBuilder.fromUri(uri);
                request.getQueryParams().forEach((k, l) -> builder.replaceQueryParam(
                        URLEncoder.encode(k, StandardCharsets.UTF_8),
                        l.stream().map(v -> URLEncoder.encode(v, StandardCharsets.UTF_8)).toList()
                ));
                builder.queryParam(
                        URLEncoder.encode(config.getName(), StandardCharsets.UTF_8),
                        URLEncoder.encode(config.getValue(), StandardCharsets.UTF_8)
                );
                final var newUri = builder.build(true).toUri();
                final var newRequest = exchange.getRequest().mutate().uri(newUri).build();
                return chain.filter(exchange.mutate().request(newRequest).build());
            }