Merge "Improve registerRouteCallback() javadoc" into main

    /**

     * Registers a callback to discover routes and to receive events when they change.

     *

     * <p>Clients can register multiple callbacks, as long as the {@link RouteCallback} instances

     * are different. Each callback can provide a unique {@link RouteDiscoveryPreference preference}

     * and will only receive updates related to that set preference.

     *

     * <p>If the specified callback is already registered, its registration will be updated for the

     * given {@link Executor executor} and {@link RouteDiscoveryPreference discovery preference}.

     *

     * <p>{@link #getInstance(Context) Local routers} must register a route callback to register in

     * the system and start receiving updates. Otherwise, all operations will be no-ops.

     *

     * <p>Any discovery preference passed by a {@link #getInstance(Context, String) proxy router}

     * will be ignored and will receive route updates based on the preference set by its matching

     * local router.

     */

    public void registerRouteCallback(

            @NonNull @CallbackExecutor Executor executor,