Is your feature request related to a problem?
In order to build a better picture of overall network health, the number of active nodes that have successfully submitted for each epoch should be stored and tracked.

Describe the solution you'd like
A redis set can be created that captures unique slot ids that have submitted for each epoch. This set can later be referenced to find out the number of active nodes.

Describe alternatives you've considered
I may be possible to get an accurate number of active nodes directly from the submission data that is already being stored in redis, but that data is expired after 30 min, and processing large amounts of submissions to get a count would be inefficient.

Additional context
N/A