Unable to receive custom keys in FCM Notification Payload after updating to V1

[matrixbot]

This issue was originally created by @mdhanif-simformsolutions at matrix-org/sygnal#393.

Hey,
we are using push notification using sygnal, recently we encountered notifications were disabled as firebase has deprecated and it's recommended to use V1 api's.
So we have upgraded our Sygnal Version to the latest one v0.15.0 and there were changes regarding how we receive payload in the latest version which we found from :- https://github.com/matrix-org/sygnal/blob/main/docs/applications.md#api-v1

Now before upgrading sygnal to latest version our content used to be like this :-

....Some keys 
"sender_display_name": "Major Tom",
  "content": {
    "msgtype": "m.text",
    "body": "I'm floating in a most peculiar way.",
    "format": "org.matrix.custom.html",
    "rel_type": "m.thread",
    "m.new_content": {
    "body": "some text",
    "format": "some format",
    "rel_type": "some rel type"
    }
  },
  "room_id": "!slw48wfj34rtnrf:example.org"
...Some other keys

Now but with the new Version we don't get all the keys :-

....Some keys 
"sender_display_name": "Major Tom",
"content_msgtype": "m.text",
"content_body": "I'm floating in a most peculiar way.",
"content_format": "org.matrix.custom.html",
// Missing all other keys as well as new content 
"room_id": "!slw48wfj34rtnrf:example.org"
...Some other keys

This is how I add a pusher :-

matrixSessionFactory.getSession()?.pushersService()?.addHttpPusher(
            HttpPusher(
                pushkey = "fcmToken",
                appDisplayName = "App name",
                appId = "appId",
                profileTag = "",
                lang = "en",
                deviceDisplayName = "Display Name",
                deviceId = "Device Id",
                url = "appUrl",
                enabled = true,
                append = true,
                withEventIdOnly = false
            )
        )

Can you please share if I have missed anything or if this has been removed ?

[matrixbot]

This comment was originally posted by @devonh at matrix-org/sygnal#393 (comment).

This has been removed in the current version due to the limitations of the new Firebase API.
If this functionality is required for your use case, feel free to PR the necessary changes to get things working.

The team has nothing against bringing it back, we just don't have any time to work on this ourselves.