How to universally modify android web view request and response headers?

Question

Android

WebView request and response headers need to be modified. I found a way through dontcry2013.github.io/2016/03/11/android-webview-c... but in this way it turns out only to process get requests, access to the body of post requests could not be done.
Is there a not very complicated way to wedge into the process of sending a request and receiving a response for a little modification? Without a strong deepening into the wilds of android?
I need something like https://addons.mozilla.org/ru/firefox/addon/header... but for web view and only in my application