Allow override of discovery URL via ConfigMap

Signed-off-by: Andrew Keesler <akeesler@vmware.com>

- Seems like the next step is to allow override of the CA bundle; I didn't
  do that here for simplicity of the commit, but seems like it is the right
  thing to do in the future.

deploy/deployment.yaml

@@ -24,6 +24,8 @@ metadata:
 data:
   #@yaml/text-templated-strings
   placeholder-name.yaml: |
+    discovery:
+      url: (@= data.values.discovery_url @)
     webhook:
       url: (@= data.values.webhook_url @)
       caBundle: (@= data.values.webhook_ca_bundle @)

deploy/values.yaml

@@ -12,3 +12,5 @@ image_tag: #! e.g. latest
 
 webhook_url: #! e.g., https://example.com
 webhook_ca_bundle: #! e.g., LS0tLS1CRUdJTiBDRVJUSUZJQ0F...
+
+discovery_url: #! e.g., https://example.com