A simple class to decode a JWT token into a dictionary and/or extract the expiration date epoch.
NSString* token = @"...";
NSDictionary* decodedDictionary = [JWTDecoder decodePayloadFromJWTToken:token];
NSString* token = @"...";
NSString* expirationEpoch = [JWTDecoder expirationEpochFromJWTToken:token];