7.1.0: Breaking change ServletOAuth2AuthorizedClientExchangeFilterFunction#authorizeClient for @Async methods

[Bego-jon28]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Create a WebClient with ServletOAuth2AuthorizedClientExchangeFilterFunction

public WebClient webClient(WebClient.Builder webClientBuilder, OAuth2AuthorizedClientManager authorizedClientManager) {
    ServletOAuth2AuthorizedClientExchangeFilterFunction oauth2Client = new ServletOAuth2AuthorizedClientExchangeFilterFunction(authorizedClientManager);
    oauth2Client.setDefaultClientRegistrationId("default-oauth");
    return webClientBuilder.apply(oauth2Client.oauth2Configuration()).build();
  }

Later if you execute a request the reauthorizeClient is called but stepped out now earlier due

		if (servletRequest == null || servletResponse == null) {
			return Mono.empty();
		}

we use a method annotated mit @Async.

  
    @Async
    public CompletableFuture<EchoResult> getBearer()  {
        var uriComponents = UriComponentsBuilder.newInstance()
                .scheme("https")
                .host("echo.free.beeceptor.com")
                .build();

        EchoResult body;

        try {
            body = webClient.get()
                    .uri(uriComponents.toUri())
                    .retrieve()
                    .bodyToMono(EchoResult.class)
                    .block();
        } catch (RuntimeException ex) {
             throw new IllegalArgumentException(ex);
        }

        return CompletableFuture.completedFuture(body);
    }

If we use without @Asyncthe authorization works

Expected behavior
Authorization works without servletRequest and servletResponse because addToAttributes handle the nullify values.

Links

• Introdurced with Enable Null checking in spring-security-oauth2-client via JSpecify #17819: baad23c#diff-53f1e59fadb03a0bce1790158ad5ccd28f6f5aa7f4459be4da79f1c00b06b1afR494

[cbertoldi]

This duplicates the issue #19324.