users service: add sessions (#17744)

* users: add cache to service

* reflect review comments

web/handlers.go

@@ -206,7 +206,7 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	if token != "" && tokenLocation != app.TokenLocationCloudHeader && tokenLocation != app.TokenLocationRemoteClusterHeader {
 		session, err := c.App.GetSession(token)
-		defer app.ReturnSessionToPool(session)
+		defer c.App.ReturnSessionToPool(session)
 
 		if err != nil {
 			c.Logger.Info("Invalid session", mlog.Err(err))