Manual Redirect URI

[sada1993]

I wanted the ability to manually set the redirect uri to another website on logout. This should be possible through the returnTo portion of the query string. Looking intologout_url() I noticed that the returnTo parameter is set by the following piece of code:

utils::URLencode(redirect_uri, reserved = TRUE)

I wanted to implement an override here so that instead of using the default global variable set in auth0_ui we can pass the redirect url manually into logout_url().

There are potentially two ways of implementing this,

1. A function parameter logout_url <- function(redirect_uri = NULL){...}
2. An additional parameter stored in the YML file

If there are any other methods to achieve this let me know, would be more than happy to put up a PR for this.