Instructions to upgrade iOS SDK version to 8.0

When upgrading from an older SDK version to version 8.0, several changes have to be applied in your application. Although it is still possible to use the old API's we recommend to update to the new API's since the old ones will be removed in the next big update of the SDK.

Removed API's

`ONGUserClient`

registerUser:delegate: ==> registerUserWithIdentityProvider:scopes:delegate: user registration is now accepting optional identity provider argument.
userClient:didRegisterUser: ==> userClient:didRegisterUser:info: additional info parameter was added. The parameter is optional and used only when using Custom Registration.

Renamed API's

`ONGRegistrationDelegate`

userClient:didReceiveRegistrationRequestChallenge: ==> userClient:didReceiveBrowserRegistrationChallenge:
ONGRegistrationRequestChallenge ==> ONGBrowserRegistrationChallenge
ONGRegistrationRequestChallengeSender ==> ONGBrowserRegistrationChallengeSender

Deprecated API's

ONGResourceRequest

ONGParametersEncodingPropertyList will be removed in the next major release.