ResourceNotificationPolicy implementation needs a rethink

[pacphi]

The design of ResourceNotificationPolicyExecutorTask and ResourceNotificationPolicy only really allow for existence matching. Label values in ResourceEmailMetadata are just email accounts which have an email domain appended.

What if we wanted to apply multiple labels to a resource and then find all resources matching a selector (which could be a combination of label key-value pair conditions), then notify an owner/designee? See selector requirement examples in table here.

The current implementation does not support this use case.

What we really want to be able to do is to notify someone (a notifyee) of a resource matching a selector.

So, maybe, if we consistently applied a label key notifyee where the value is always an email account or distribution-list alias stripped of its domain along with any other combo of label key-value pairs to a supported ResourceType, we could use that to send notifications. Perhaps we make a notifyee label-key configurable (per policy definition)?