Logout Redirection (#365)

- fixing up the logout redirection to keycloak (note, this url has to be in the verified url in the client)

handlers.go

@@ -326,9 +326,10 @@ func (r *oauthProxy) logoutHandler(w http.ResponseWriter, req *http.Request) {
 
 	// @check if we should redirect to the provider
 	if r.config.EnableLogoutRedirect {
-		sendTo := fmt.Sprintf("%s/protocol/openid-connect/logout?redirect_uri=%s",
-			strings.TrimSuffix(r.config.DiscoveryURL, "/.well-known/openid-configuration"), redirectURL)
-
+		sendTo := fmt.Sprintf("%s/protocol/openid-connect/logout", strings.TrimSuffix(r.config.DiscoveryURL, "/.well-known/openid-configuration"))
+		if redirectURL != "" {
+			sendTo = fmt.Sprintf("%s?redirect_uri=%s", sendTo, url.QueryEscape(redirectURL))
+		}
 		r.redirectToURL(sendTo, w, req)
 
 		return