added redirectUri parameter to GetAuthorizationUrl

[bcwood]

By specifying the return_url parameter to /authorize, the user will automatically be redirected back to the calling web application after authorizing access.

Instead of creating an overloaded method for this, I thought about including redirectUri as an optional parameter, but in the original implementation of GetAuthorizationUrl, you're using /connect instead of /authorize, but I couldn't find any documentation on /connect. Perhaps this is an old endpoint that is only left open for backwards compatibility?