How to access Capacitor bridge in a class

[elenche]

Hi everyone.
I'm trying to figure out how to use the Capacitor Android bridge in a class, not in a plugin. Specifically, I've created a native NotificationServiceExtension class per OneSignal docs so the app can receive background/data notifications. The notifications are received correctly in the class, so now I want to inform the JS layer of the received notification. Per Capacitor docs, we should be able to achieve this by calling bridge.triggerJSEvent("myCustomEvent", "document", "{ 'dataKey': 'dataValue' }");.
However when this line is executed, I get an error:
Attempt to invoke virtual method 'void com.getcapacitor.Bridge.triggerJSEvent(java.lang.String, java.lang.String, java.lang.String)' on a null object reference.

android/app/src/main/java/com/mycompany/myapp/NotificationServiceExtension.java:

package com.mycompany.myapp;

// Import bridge
import com.getcapacitor.Bridge;
import com.onesignal.notifications.IDisplayableMutableNotification;
import com.onesignal.notifications.INotificationReceivedEvent;
import com.onesignal.notifications.INotificationServiceExtension;
import com.onesignal.debug.internal.logging.Logging;

public class NotificationServiceExtension implements INotificationServiceExtension {

    // TODO: Initialize bridge

    @Override
    public void onNotificationReceived(INotificationReceivedEvent event) {
        IDisplayableMutableNotification notification = event.getNotification();

        Logging.info(String.format("NotificationServiceExtension::onNotificationReceived: notificationId=%s, additionalData=%s", notification.getNotificationId(), notification.getAdditionalData()), null);

        // TODO: Use bridge 
        // bridge.triggerJSEvent("myCustomEvent", "document", "{ 'dataKey': 'dataValue' }");
    }
}

android/app/src/main/AndroidManifest.xml

<?xml version='1.0' encoding='utf-8'?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme" android:usesCleartextTraffic="true">
        <activity android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|smallestScreenSize|screenLayout|uiMode" android:exported="true" android:label="@string/title_activity_main" android:launchMode="singleTask" android:name=".MainActivity" android:theme="@style/AppTheme.NoActionBarLaunch">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <meta-data android:name="com.onesignal.NotificationServiceExtension" android:value="com.skoop.terminal2.NotificationServiceExtension" /> 
    </application>
    <uses-permission android:name="android.permission.INTERNET" />
</manifest>

Thanks for your help!