message_id is not always an int

[yannleretaille]

Thanks for merging and fixing the tests!
The issue with message_id still persists however. Maybe a way to handle it would be to mark it as None when "fake_message_id" is returned and Some(u64) when its an actual number. The downside would be that we loose the information that this is a dry_run, but maybe that could be added to the Response struct.
The fix could be implemented by interpreting message_id as a string and then do:
let message_id_int: u64 = message_id.parse().ok();

[vishy1618]

I did not understand this requirement. Why would you want it to be string when doing a dry_run?

[yannleretaille]

I do not want it to be string. GCM returns a string ("fake_message_id") when doing a dry_run. The crate is not handling that case right now and panics trying to convert the string into a u64. Thats why on my local version, I changed the type of message_id to string, but the best way to fix it is imho to parse it as proposed.

[vishy1618]

Addressed this with 0.2.0 using serde::json custom deserialising for that field.