Access headers for Messaging.send response?

[fredrikjaxwall]

The docs for Cloud Messaging states that one should

Honor the Retry-After header if it is included in the response from the FCM Connection Server

However, it doesn't seem like the headers are accessible when using Messaging.send in firebase-admin-node?

While it does seem like the SDK has some internal retry-mechanisms, I assume these won't cover cases where Retry-After is more than (at most) a few minutes into the future.

Is there a way to access the headers to be able to handle these cases?

Thanks!