Document how to set DNS Group value for DNS Operator.

[philbrookes]

Kuadrant CR is not a good place for this value, as it may eventually evolve to be a multi-tenant solution where many group values could exist in one cluster.

The best solution here may be to give the user the commands to write the group directly to the configmap used by the DNS Operator.

so something like:

• kubectl patch configmap -p '{"data": {"groupID": "groupName"}}'
• kubectl rollout restart dns-operator
• watch for panic, if the groupName is bad (i.e. has a ;)