Fixes to Concurrency

This contains an important fix for concurrency that could potentially lead to crashes.

Important Fix For HttpRequest

Fixes an important bug in HttpRequest where some overloads didn't use the provided encoder.

ApiKit-OAuth & Bug Fixes

• Split OAuth into its own package
• Important fixes to concurrency for the library as a whole.

Important fix when cancelling operation.

Fixes a bug when an operation is cancelled completion is called more then once.

ApiInterceptor Improvements & Bug Fixes

ApiInterceptor can now cancel requests by passing nil to onNewRequest.
OAuthInterceptor fixed bug where could lock API.

Fix for OAuthInterceptor

OAuthInterceptor semaphore could possibly get locked

Fix for OAuthProvider

OAuthProvider should not set Authorization correctly

DefaultGoogleAuthProvider Improvements

DefaultGoogleAuthProvider init scope changed to public to allow subclassing.

Improvements to DefaultGoogleAuthProvider

DefaultGoogleAuthProvider is now open

Easily allows the the switch from accessToken to idToken.

Improvements to LogInterceptor

Added Headers to LogInterceptor