The registration step registers the app with the device's system and returns a registration id
 import { Push, RegistrationEventResponse} from "ionic-native";
        //the push element is created in the initialization example
        push.on("registration", async (response: RegistrationEventResponse) => {
                    //The registration returns an id of the registration on your device
                    RegisterWithWebApi(response.registrationId);
    
        });