[spike] Define how to handle metrics events in the DNS Operator

[philbrookes]

As we are discussing the addition of some metrics to the DNS Operator, which could cause a degree of chaos within the codebase, let's take some time to investigate the best practices used in other operators to handle metrics cleanly and in an extendible manner.

Once we have an idea of the options we can make a decision as a team on which way seems the most maintainable.