Microprofile Rest Client Error javax.ws.rs.WebApplicationException: Unknown error, status code 405

Question

I'm very new to RestAPI and I'm stuck with this problem. I'm trying to send a request using the Rest Client to my Wildfly Server, but I get this error:

javax.ws.rs.WebApplicationException: Unknown error, status code 405

    at org.jboss.resteasy.microprofile.client.DefaultResponseExceptionMapper.toThrowable(DefaultResponseExceptionMapper.java:21)
    at org.jboss.resteasy.microprofile.client.ExceptionMapping$HandlerException.mapException(ExceptionMapping.java:41)
    at org.jboss.resteasy.microprofile.client.ProxyInvocationHandler.invoke(ProxyInvocationHandler.java:153)
    at jdk.proxy2/jdk.proxy2.$Proxy29.easy(Unknown Source)
    at UserResourceImplIT.add(UserResourceImplIT.java:30)

This is my test:

import java.net.URI;
import java.util.Date;

import javax.ws.rs.core.Response;


import org.eclipse.microprofile.rest.client.RestClientBuilder;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import com.tech11.startingasbackend.business.boundary.UserResource;
import com.tech11.startingasbackend.business.entity.CreateUserDTO;

public class UserResourceImplIT {

    private UserResource client;

     @BeforeEach
     public void init() {
     URI uri = URI.create("http://localhost:8080/starter");
     this.client = RestClientBuilder
     .newBuilder()
     .baseUri(uri)
     .build(UserResource.class);
     }

     @Test
     public void add() {
        Response response = this.client.easy("HELLO");

     }
}

My Interface:

public interface UserResource {

    @POST
    Response easy(String message);

}

And my implementation:

public class UserResourceImpl implements UserResource {
   
    @Override
    public Response easy(String message) {
       return Response.ok().build();
    }

When I remove the @Path("/user") annotation from my Interface, the bug disappears, but nothing is posted in the database. Does anyone know what I'm missing and why this error occurs or how to proceed?