Grails 4 Oauth2 token call another service(grails app)

I'm implementing a Grails4 user app that simply manages the user and generates the oauth2 access_token.

My requirement is to get the oauth2 token from the user app and use this token to call services on my other grails app.

Now I can successfully get the oauth token from the user app. using:

dependencies {
    compile 'org.grails.plugins:spring-security-oauth2-provider:4.0.0-RC1'
}

Does someone know how to config the service Grails app, which points to my user auth app, and authenticate the oauth2 token to control the API access.

Much appreciated! I'm really stuck on this one.