IOS notification subtitle (multiline title)

[ori9998]

Hello, according to the firebase docs of REST api,
ios subtitle is no longer supported.

However, in the legacy HTTP Server Protocol
ios subtitle is supported.

Is there a way to implement the multiline title?
Without the official support with the notification field, I've tried using notifee to use the data field instead.

The flow that it worked in the foreground notification:

1. send the subtitle string inside the data payload
2. use notifee to display subtitle
3. Yay! The multiline title works

This method works from in the foreground notification, but in the background, I've tried implementing notifee in index.js, but setBackgroundMessageHandler is not firing.

Any help please?

index.js
`import 'react-native-get-random-values';
import React from 'react'

import {AppRegistry} from 'react-native';
import messaging from '@react-native-firebase/messaging';
import App from './App';
import {name as appName} from './app.json';

messaging().setBackgroundMessageHandler(async remoteMessage => {
console.log('Message handled in the background!', remoteMessage);
await notifee.displayNotification({
title: remoteMessage.notification.title,
subtitle: remoteMessage.data.subtitle,
body: remoteMessage.notification.title,
data: remoteMessage.data,
ios: {
foregroundPresentationOptions: {
sound: true,
banner: true,
list: true,
},
}
})
});

function HeadlessCheck({ isHeadless }) {
console.log('headless check')
if (isHeadless) {
console.log("Headless");
// App has been launched in the background by iOS, ignore
return null;
}

return <App />;

}

AppRegistry.registerComponent(appName, () => HeadlessCheck);

`

Payload
`const payload = {
token: 'aaa',

            notification: {
                title: `hello`,
                body: "this is body!",
            },
            data: {
                screen: 'HomeScreen',
                subtitle: 'subtitle'
            },
            apns: {
                payload: {
                  aps: {
                    contentAvailable: true,
                  },
                },
            }
        }

         admin.messaging().send(payload).then((response) => {
            console.log('Successfully sent message:', response);
            return {success: true};
        }).catch((error) => {
            console.log('e', error)
            return {error: error.code};
        });`