As a customer user, I need to be able to access the total notebook usage for my account so I can track expected monthly charge.

This story is to create a Prometheus recording rule to calculate the billing metric per cluster in RHODS. The metric will be # of notebook sessions. The current plan is to check the number at a regular frequency and record the number with a date/time stamp. The total hours / month would then be calculated in a SWatch equation.

2/11/21: As part of this story, we also would like to capture metrics for resource consumption - CPU and memory. Based on some discussions, we might consider a pricing element related to resource consumption, so we'd like to have these metrics available.