Ionic Push Notification Payload

Does Ionic push notification allow customized payloads? For example, I was trying to send a JSON like this through the ionic push notification service:

    "tokens": ["DEV-6606fbd0-3d63-4439-bcb5-5b914c71edb3"],
    "profile": "security_profile",
        "message": "Test",
        "payload": {"notification_id": "1",
        "notification_type": "new device",
        "severity": "low",
        "icon": "",
        "text": "New Device added"

When I tried to get notification.payload, I get nothing. Also, to get the “message” field, I have to do notification.text instead of notification.message. Is there a developed documentation on the fields that are allowed and what everything’s mapped to?