Support customizable callback url-scheme.

[noppefoxwolf]

No description provided.

[meteochu]

Apologies for the late review, added a comment requesting change on the method signature to prevent duplication of the code. Using an optional String for the callback url scheme can help prevent code duplication.

[meteochu]

Instead of duplicating the method signature with a customizable callback URL, this should use an optional callback.

func authorizeSSO(
    withCallbackURLScheme urlScheme: String? = nil, 
    success: SSOTokenSuccessHandler, 
    failure: FailureHandler? = nil
) {
    guard let client = client as? SwifterAppProtocol else { 
        // handle error
        return
    } 
    let urlScheme = urlScheme ?? "swifter-\(client.consumerKey)"
    // ...
}