Add the default standardized "User-Agent" for API requests handled by OkHttp

[luongvo]

Why

According to the real project use case, we might need to send a standard "User-Agent" for API request headers. While this is supported by default iOS with Alamofire, Android can use this small OkHttp extension to standardize sending the same User-Agent structure as iOS https://github.com/AckeeCZ/android-user-agent.

For example, Tapito/2.5.8 (com.tapmedia.tapito.debug; build:1520; Android 7.0; Model:Nexus 5X) okhttp/3.2.0

Who Benefits?

Developers, PMs