Liferay Jax-RS : Unable to call simple REST apis, getting 403 and 405

I am using Liferay 7.3.

Trying to build Rest APIs using JAX-RS and I have generated token by following official documentation here https://help.liferay.com/hc/en-us/articles/360018166411-JAX-RS#using-oauth-20-to-invoke-a-jax-rs-web-service

getting 403 [Forbidden] for @GET and 405 [method not allowed] for @POST

package com.liferay.jaxrstest.application;

import java.util.Collections;
import java.util.Set;

import javax.ws.rs.*;
import javax.ws.rs.core.Application;
import javax.ws.rs.core.MediaType;

import org.osgi.service.component.annotations.Component;
import org.osgi.service.jaxrs.whiteboard.JaxrsWhiteboardConstants;

@Component(
    property = {
        JaxrsWhiteboardConstants.JAX_RS_APPLICATION_BASE + "=/greetings",
        JaxrsWhiteboardConstants.JAX_RS_NAME + "=Greetings.Rest"
    },
    service = Application.class
)
public class LiferaxJaxRsTestApplication extends Application {

    public Set<Object> getSingletons() {
        return Collections.<Object>singleton(this);
    }

    @GET
    @Produces("text/plain")
    public String working() {
        return "It works!";
    }

    @GET
    @Path("/morning")
    @Produces("text/plain")
    public String hello() {
        return "Good morning!";
    }

    @POST
    @Path("/morning")
    // @Produces("text/plain")
    // @Consumes("application/json")
    @Produces(MediaType.APPLICATION_JSON)
    @Consumes(MediaType.APPLICATION_JSON)
    public String hello(User user) {
        return "Good morning!" + user.getFirstName();
    }
}

class User {

    private String firstName;
    
    public User(String firstName) {
        this.firstName = firstName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    
}