OnProxyAuthorization is a TIdProxyOnAuthorization property that represents the event handler signalled when an HTTP client selects an authentication class to be used when session or proxy authentication is required for a connection. OnProxyAuthorization is signalled prior to triggering the OnAuthorization event handler. 

AuthenticationClass is the class instance to be used to perform authentication for the mechanisms required in an HTTP request. 

AuthInfo is the header values to be be used in the HTTP response that includes the authentication results. 

Applications must assign a procedure to the event handler to allow responding to the event notification, or to allow the in-process authentication permitted using TIdHTTP.HTTPOptions.