JWT, JWK and JWA separation.

[lolgear]

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Issue Info

Info	Value
Platform Name	e.g. ios / osx / tvos / watchos
Platform Version	e.g. 8.0
CocoaLumberjack Version	e.g. 2.3.0
Integration Method	e.g. carthage / cocoapods / manually
Xcode Version	e.g. Xcode 7.3
Repro rate	e.g. all the time (100%) / sometimes x% / only once
Demo project link	e.g. link to a demo project that highlights the issue

Issue Description and Steps

Although JWT implementation is not a rocket science, it has become huge. I would like to separate implementations of key extraction ( JWK ), jWT handling and algorithms implementations ( JWA ).

So, at the end we would have different targets for testing and it will reduce API and elements coupling.