Allow to change URL/method in ClientRequest.Builder

This commit exposes the ClientRequest's URL and HttpMethod fields via a
setter, so that they can be changed more easily in a request that was
created via ClientRequest.from(ClientRequest).

Issue: SPR-16093

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientRequest.java

@@ -134,6 +134,20 @@ public interface ClientRequest {
 	 */
 	interface Builder {
 
+		/**
+		 * Set the method of the request.
+		 * @param method the new method
+		 * @return this builder
+		 */
+		Builder method(HttpMethod method);
+
+		/**
+		 * Set the url of the request.
+		 * @param url the new url
+		 * @return this builder
+		 */
+		Builder url(URI url);
+
 		/**
 		 * Add the given header value(s) under the given name.
 		 * @param headerName  the header name

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultClientRequestBuilder.java

@@ -49,16 +49,16 @@ import org.springframework.web.reactive.function.BodyInserters;
  */
 class DefaultClientRequestBuilder implements ClientRequest.Builder {
 
-	private final HttpMethod method;
-
-	private final URI url;
-
 	private final HttpHeaders headers = new HttpHeaders();
 
 	private final MultiValueMap<String, String> cookies = new LinkedMultiValueMap<>();
 
 	private final Map<String, Object> attributes = new LinkedHashMap<>();
 
+	private HttpMethod method;
+
+	private URI url;
+
 	private BodyInserter<?, ? super ClientHttpRequest> inserter = BodyInserters.empty();
 
 
@@ -67,6 +67,19 @@ class DefaultClientRequestBuilder implements ClientRequest.Builder {
 		this.url = url;
 	}
 
+	@Override
+	public ClientRequest.Builder method(HttpMethod method) {
+		Assert.notNull(method, "'method' must not be null");
+		this.method = method;
+		return this;
+	}
+
+	@Override
+	public ClientRequest.Builder url(URI url) {
+		Assert.notNull(url, "'url' must not be null");
+		this.url = url;
+		return this;
+	}
 
 	@Override
 	public ClientRequest.Builder header(String headerName, String... headerValues) {