var additionalTokenRequestParams : [String : String]? Any additional parameters for the token request.
var additionalRefreshTokenBodyParams : [String : String]? Ignore if the server not provide a refresh token. Any additional HTTP body parameters for the token refresh request. The key/value pairs for “refresh_token” and “grant_type” are handled internally when an
authenticatedRequest(for:numberOfRetries:) is made.var scopes: String? The scopes you want your app to be authorized for, separated by spaces.
var authHeaderTokenType : String? Some APIs may use a different key for their authorization header’s token type than the one provided by the token request response.