Reactive Routes: invalid value for a converted @Param results in 500 instead of 400 #57828

Describe the bug

A reactive route parameter of a converted type (@Param Integer, Long, Boolean, …) results in 500 Internal Server Error when the request contains a value that cannot be converted, e.g. ?value=abc for an Integer. The generated handler catches the conversion failure and rethrows it as an IllegalArgumentException (ReactiveRoutesProcessor), which ends up in QuarkusErrorHandler as a 500.

Expected behavior

400 Bad Request, since the value comes from the client.

Actual behavior

500 Internal Server Error:

ERROR [io.quarkus.vertx.http.runtime.QuarkusErrorHandler] (vert.x-eventloop-thread-1) HTTP Request to /square?value=abc failed, error id: ...: java.lang.IllegalArgumentException: Error converting parameter #0 of method org.acme.Routes.square()
...
Caused by: java.lang.NumberFormatException: For input string: "abc"

How to Reproduce?

1. Create a project:

   mvn io.quarkus.platform:quarkus-maven-plugin:3.40.1.1:create \
       -DprojectGroupId=org.acme -DprojectArtifactId=routes-repro \
       -Dextensions=reactive-routes -DnoCode
   cd routes-repro

2. Add src/main/java/org/acme/Routes.java:

   package org.acme;
   
   import io.quarkus.vertx.web.Param;
   import io.quarkus.vertx.web.Route;
   
   public class Routes {
   
       @Route(path = "/square", methods = Route.HttpMethod.GET)
       String square(@Param Integer value) {
           return String.valueOf(value * value);
       }
   }

3. Run ./mvnw quarkus:dev.
4. Send requests:

   curl -s -o /dev/null -w "%{http_code}\n" 'localhost:8080/square?value=3'     # 200
   curl -s -o /dev/null -w "%{http_code}\n" 'localhost:8080/square?value=abc'   # 500

The same result with 4.0.0.Beta1 instead of 3.40.1.1 in step 1.

Output of uname -a or ver

Linux 6.18.54.1-microsoft-standard-WSL2 x86_64 GNU/Linux

Output of java -version

OpenJDK 21.0.12.1 (Temurin-21.0.12.1+1)

Quarkus version or git rev

3.40.1.1, 4.0.0.Beta1, main (5e98984)

Build tool (ie. output of mvnw --version or gradlew --version)

Apache Maven 3.9.9

Additional information

Similar to #57824, which covers malformed JSON in @Body parameters. I'll open a PR with a fix and a test.