Add list of know working OpenStack clouds

contrib/terraform/openstack/README.md

@@ -8,6 +8,23 @@ Openstack.
 This will install a Kubernetes cluster on an Openstack Cloud. It should work on
 most modern installs of OpenStack that support the basic services.
 
+### Known compatible public clouds
+- [Auro](https://auro.io/)
+- [BetaCloud](https://www.betacloud.io/)
+- [CityCloud](https://www.citycloud.com/)
+- [DreamHost](https://www.dreamhost.com/cloud/computing/)
+- [ElastX](https://elastx.se/)
+- [EnterCloudSuite](https://www.entercloudsuite.com/)
+- [FugaCloud](https://fuga.cloud/)
+- [Ultimum](https://ultimum.io/)
+- [VexxHost](https://vexxhost.com/)
+- [Zetta](https://www.zetta.io/)
+
+### Known incompatible public clouds
+- OVH: No router support
+- Rackspace: No router support
+- T-Systems / Open Telekom Cloud: requires `wait_until_associated`
+
 ## Approach
 The terraform configuration inspects variables found in
 [variables.tf](variables.tf) to create resources in your OpenStack cluster.