Message send from client to send notif using FCM service.
Depends on D12769
Tested in D12772.
This could take only HIGH and NORMAL values but wanted to make it in-sync with Rust types
I'd rather make it more specific in JS, if Rust doesn't support the specificity
In Rust it's technically a string, but parsing will fail (or at least ignore, in D12767 it's set to None) if it's not one of the above, so I'd use +priority: 'NORMAL' | 'HIGH'. here
makes sense, I'll update this to +priority: 'NORMAL' | 'HIGH'. before landing
improve type