fix: fix RouterLabelRestTemplateInterceptor add response headers exception with httpclient5 (#1376)

Co-authored-by: Haotian Zhang <skyebefreeman@qq.com>
Co-authored-by: gzoldou <gzoldou@163.com>

CHANGELOG.md

@@ -4,3 +4,4 @@
 - [feat:upgrade jackson version.](https://github.com/Tencent/spring-cloud-tencent/pull/1258)
 - [fix:fix ApplicationContextAwareUtils NPE bug.](https://github.com/Tencent/spring-cloud-tencent/pull/1296)
 - [feat:upgrade jacoco version.](https://github.com/Tencent/spring-cloud-tencent/pull/1307)
+- [fix: fix RouterLabelRestTemplateInterceptor add response headers exception with httpclient5.](https://github.com/Tencent/spring-cloud-tencent/pull/1376)

spring-cloud-starter-tencent-polaris-router/src/main/java/com/tencent/cloud/polaris/router/resttemplate/RouterLabelRestTemplateInterceptor.java

@@ -44,6 +44,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import org.springframework.core.Ordered;
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpRequest;
 import org.springframework.http.client.ClientHttpRequestExecution;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
@@ -103,7 +104,8 @@ public class RouterLabelRestTemplateInterceptor implements ClientHttpRequestInte
 		ClientHttpResponse response = clientHttpRequestExecution.execute(request, body);
 
 		if (!CollectionUtils.isEmpty(request.getHeaders().get(RouterConstant.ROUTER_LABEL_HEADER))) {
-			response.getHeaders().addAll(RouterConstant.ROUTER_LABEL_HEADER, Objects.requireNonNull(request.getHeaders()
+			HttpHeaders responseHeaders = HttpHeaders.writableHttpHeaders(response.getHeaders());
+			responseHeaders.addAll(RouterConstant.ROUTER_LABEL_HEADER, Objects.requireNonNull(request.getHeaders()
 					.get(RouterConstant.ROUTER_LABEL_HEADER)));
 		}