Allows the configuration of additional Play Routers.

Typically, this will be a Router generated from a Play Router or a akka-grpc generated Play Router.

Once you declare a Router, you may need to define it's prefix to indicate on which path it should be available.

new LagomApplication(context) with AhcWSComponents with LocalServiceLocator {
  override def lagomServer: LagomServer =
    serverFor[MyService](new MyServiceImpl)
      .additionalRouter(new HelloWorldRouter().withPrefix("/hello"))
}

You don't need to configure a prefix if the Router has it pre-configured. A akka-grpc generated Play Router, for instance, has its prefix already defined by the gRPC descriptor and doesn't need to have its prefix reconfigured.