Additional parameters to add to each server request

[AlexLobaciov]

Summary:
For every request that Salt Edge Authenticator performs to the server, it is necessary to additionally provide some important information for the Audit log.

Task:

• Add the User agent request header (application and version) for all REST requests
• Add the User agent request header (application and version) for WebView requests
• Update documentation and examples.

[ConstantinKV]

good example https://github.com/danielceinos/Cooper/blob/master/cooper/src/main/java/com/danielceinos/cooper/CooperInterceptor.kt

[ConstantinKV]

wkWebView.customUserAgent = "IOS agent"