Provide context for Reactive Rest Client exceptions

We now add the exact method that caused the exception
in order to make it easier for users to identity where
the exception is coming from

Fixes: quarkusio#22090

independent-projects/resteasy-reactive/client/runtime/src/main/java/org/jboss/resteasy/reactive/client/impl/RestClientRequestContext.java

@@ -10,6 +10,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.annotation.Annotation;
+import java.lang.reflect.Method;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.net.URI;
@@ -46,6 +47,8 @@
  */
 public class RestClientRequestContext extends AbstractResteasyReactiveContext<RestClientRequestContext, ClientRestHandler> {
 
+    private static final String MP_INVOKED_METHOD_PROP = "org.eclipse.microprofile.rest.client.invokedMethod";
+
     private final HttpClient httpClient;
     // Changeable by the request filter
     String httpMethod;
@@ -140,8 +143,16 @@ public void abort() {
     protected Throwable unwrapException(Throwable t) {
         var res = super.unwrapException(t);
         if (res instanceof WebApplicationException) {
-            WebApplicationException webApplicationException = (WebApplicationException) res;
-            return new ClientWebApplicationException(webApplicationException.getMessage(), webApplicationException,
+            var webApplicationException = (WebApplicationException) res;
+            var message = webApplicationException.getMessage();
+            var invokedMethodObject = properties.get(MP_INVOKED_METHOD_PROP);
+            if ((invokedMethodObject instanceof Method)) {
+                var invokedMethod = (Method) invokedMethodObject;
+                message = "Received: '" + message + "' when invoking: Rest Client method: '"
+                        + invokedMethod.getDeclaringClass().getName() + "#"
+                        + invokedMethod.getName() + "'";
+            }
+            return new ClientWebApplicationException(message, webApplicationException,
                     webApplicationException.getResponse());
         }
         return res;