#73 implement --cluster-registry-url option

docs/multiple-clusters.rst

@@ -4,4 +4,28 @@ Multiple Clusters
 
 Set the ``CLUSTERS`` environment variable to a comma separated list of Kubernetes API server URLs.
 
-TODO: how to configure authentication, registry, ..
+Cluster Registry
+================
+
+Clusters can be dynamically discovered by providing one HTTP endpoint as the cluster registry.
+Set either the ``CLUSTER_REGISTRY_URL`` environment variable or the ``--cluster-registry-url`` option to an URL conforming to:
+
+.. code-block:: bash
+
+    $ curl -H 'Authorization: Bearer mytoken' $CLUSTER_REGISTRY_URL/kubernetes-clusters
+    {
+        "items": [
+            {
+                "id": "my-cluster-id",
+                "api_server_url": "https://my-cluster.example.org"
+            }
+        ]
+    }
+
+The cluster registry will be queryied with an OAuth Bearer token, the token can be statically set via the ``OAUTH2_ACCESS_TOKENS`` environment variable.
+Example:
+
+.. code-block:: bash
+
+    $ token=mysecrettoken
+    $ docker run -it -p 8080:8080 -e OAUTH2_ACCESS_TOKENS=read-only=$token hjacobs/kube-ops-view --cluster-registry-url=https://cluster-registry.example.org