AWS Pinpoint: Set APNS "mutable-content": 1

There is no documentation but this worked for me after some trial and error:

var payload = {
    "aps": {
        "alert": {
            "title": "Bold text in the notification",
            "body": "Second line in the notification"
        },
        "sound": "default",
        "mutable-content": 1
    }
};

var messageRequest = {
    Addresses: {
        [token]: {
            ChannelType: "APNS",
        },
    },
    MessageConfiguration: {
        APNSMessage: {
            RawContent: JSON.stringify(payload),
        },
    },
};

Just replace their template with RawContent and create the payload as you would normally. Can refer to apple docs on how to create the raw payload. You can also adjust content-available key using this method. Here is the link to how to create a payload with json:

https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/generating_a_remote_notification