Error: Client error: `POST https://fcm.googleapis.com/v1/projects/bmsapp-9e5de/messages:send` resulted in a `400 Bad Request` response:
{
  "error": {
    "code": 400,
    "message": "Recipient of the message is not set.",
    "status": "INVALID_ARGUMENT", (truncated...)
Response: {
  "error": {
    "code": 400,
    "message": "Recipient of the message is not set.",
    "status": "INVALID_ARGUMENT",
    "details": [
      {
        "@type": "type.googleapis.com/google.rpc.BadRequest",
        "fieldViolations": [
          {
            "field": "message",
            "description": "Recipient of the message is not set."
          }
        ]
      },
      {
        "@type": "type.googleapis.com/google.firebase.fcm.v1.FcmError",
        "errorCode": "INVALID_ARGUMENT"
      }
    ]
  }
}
Failed to send message.