Bug Report: Trigger/dashboard payload is not delivered to Android via FCM (only reaches device through overrides.providers.fcm.data)

Description

Custom payload fields sent to a push workflow are not delivered to Android via FCM. Only the notification title/body reach the device; all other payload fields are silently dropped.

The only workaround is to duplicate the fields into overrides.providers.fcm.data at trigger time. This can't be done from the dashboard, since the push step editor only exposes title and body. As a result the trigger reports success while the data never arrives on the device.

Reproduction steps

Create a workflow with a Push step configured for the FCM provider, mapping the notification to payload.title and payload.body. Then trigger the workflow with extra fields and no overrides, e.g.:

{
  "title": "New transaction",
  "body": "You have a new transaction",
  "payload": {
    "type": "transaction",
    "transaction_id": "transaction_...",
    "legal_entity_id": "legalentity_..."
  }
}

Check the Activity Feed and the received RemoteMessage on the device: the custom fields are absent, the FCM "Message created" record shows "content": null, and they never reach onMessageReceived. Re-triggering with overrides.providers.fcm.data duplicating the same fields makes the data reach the device.

Expected behavior

Custom payload fields should be deliverable to Android via FCM (mapped into the FCM data object) without requiring trigger-time provider overrides, and this should be configurable from the dashboard push step editor.

Actual behavior

Without overrides, the message is reported as sent but only title/body are delivered; all custom fields are dropped. The data only arrives when duplicated into overrides.providers.fcm.data at trigger time, for which there is no dashboard option.

Additional context

Novu SaaS (Cloud, dashboard.novu.co). Likely related to #9489, #4876, and #2644. The recently shipped "Provider content overrides" still doesn't cover passing arbitrary trigger payload into the FCM data object.