Implement /eligibleclients endpoint updates with Pub/Sub framework, for instantaneous updates to the Active List

[eric-jahn]

Instead of a current 2 hour batch processing interval for the eligible clients endpoint, the Active List will be updated in real-time on a client-by-client basis, using HSLynk's Publish/Subscribe change notification framework. This avoids the need to scan all HSLynk records for changes, and simply notifies the active list when single changes in the underlying eligibility occur, on a client-by-client basis. Work order reference: #CTA0015.

[suryayadavalli]

pub / sub implementation to sync active list real time is complete now. Eligible clients / active list should reflect the changes as soon as the scores for the client are posted / updated.

Completed and deployed.
commit id: 2d87011

[eric-jahn]

@suryayadavalli , @CTAJavier encountered some clients still in GET /eligibleclients which had been deleted. Sandeep cleared them out of /eligibleclients manually, but new ones will probably occur. Here were the IDs: https://hslynk.slack.com/archives/CAA3H13SA/p1580494500023100