Add notice to net-ilb module on routes (#1415)

* add support for routes

* boilerplate

* revert and add notice to README

* revert

* revert

* Fix README

---------

Co-authored-by: Julio Castillo <jccb@google.com>

modules/net-ilb/README.md

@@ -4,15 +4,19 @@ This module allows managing a GCE Internal Load Balancer and integrates the forw
 
 ## Issues
 
-TODO(ludoo): check if this is still the case after splitting out MIG from compute-vm
-
-There are some corner cases (eg when switching the instance template from internal service account to an externally managed one) where Terraform raises a cycle error on apply. In these situations, run successive applies targeting resources used in the template first then the template itself, and the cycle should be fixed.
+There are some corner cases where Terraform raises a cycle error on apply, for example when using the entire ILB module as a value in `for_each` counts used to create static routes in the VPC module. These are easily fixed by using forwarding rule ids instead of modules as values in the `for_each` loop.
 
+<!--
 One other issue is a `Provider produced inconsistent final plan` error which is sometimes raised when switching template version. This seems to be related to this [open provider issue](https://github.com/terraform-providers/terraform-provider-google/issues/3937), but it's relatively harmless since the resource is updated, and subsequent applies raise no errors.
+-->
 
 ## Examples
 
-### Reference existing MIGs
+- [Referencing existing MIGs](#referencing-existing-migs)
+- [Externally manages instances](#externally-managed-instances)
+- [End to end example](#end-to-end-example)
+
+### Referencing existing MIGs
 
 This example shows how to reference existing Managed Infrastructure Groups (MIGs).