Replace Tutorial TBD with REST tutorial

SIDEBAR.md

@@ -18,9 +18,9 @@ There's more to building RESTful web services than is covered here. You can cont
 
 ### Tutorials
 
-* [Tutorial TBD][tut-tbd]
+* [Designing and Implementing RESTful Web Services with Spring][tut-rest]
 
-[tut-tbd]: /guides/tutorials/tbd
+[tut-rest]: /guides/tutorials/rest
 
 ### Concepts and Technologies