Expand documentation for custom requests to cover additional use cases

Volley seems to be a nice library for a very basic usage but it seems missing (or not documented) some critical functionalities, like:

1. How can I set customer headers on request?
2. How can I read headers on response from the server?
3. How can I send a plain text or binary payload when making a POST or PUT request?
4. How can I read http status codes (200 = OK, 404 = not found, ... do you mean?)

All this in Kotlin, of course, the language google is pushing!