Default User-Agent header for all networking requests should include the App Name and Version

[pke]

Introduction

Currently the user agents used by iOS and Android for network requests differ. See https://github.com/facebook/react-native/issues/30163

For me the User-Agent is an integral parts of proper Client/Server communication for various scenarios (tailoring responses alongside Accept headers, sun-setting of endpoints, tracking, logging)

The user agent should therefore include the app name and version and be part of every requests of the fetch, XMLHttpRequest and Image APIs.

Details

iOS is already including the app name + version in all its fetch/Image requests. Android does

However on both platforms user agents can only be set on a per-request level, not globally. I propose that the networking layer includes the user agent with the appname by default on all platforms (not only iOS). The "okhttp/version" stays in the Android user agent.

I a second step a new global Networking.userAgent could allow to override the global user agent if apps need special tokens in there.

The current per-request header settings is not affected by this proposal. It stays in the hand of the app developer.

Discussion points

1. What problems could arise from changing the default user agent on Android to include the App name + version like on iOS (beside the okhttp client it already contains today)?

2. Should the global override sit on a new Networking namespace or on each fetch, XMLHttpRequest and Image individually?