WebClient exposes API for access to native request

Closes gh-25115, gh-25493

spring-test/src/main/java/org/springframework/mock/http/client/reactive/MockClientHttpRequest.java

@@ -104,6 +104,12 @@ public class MockClientHttpRequest extends AbstractClientHttpRequest {
 		return DefaultDataBufferFactory.sharedInstance;
 	}
 
+	@Override
+	@SuppressWarnings("unchecked")
+	public <T> T getNativeRequest() {
+		return (T) this;
+	}
+
 	@Override
 	protected void applyHeaders() {
 	}