compute online/offline transitions on subs-notifs side instead of relying on online/online-prev in NE status

[konstan]

There might be cases when the combined work of the API server, job-engine NE state updater, and ES-to-Kafka exporter on nuvlabox-status creates a situation where we might miss offline-to-online transition expressed as online-prev=False and online=True. Here is the example

"current-time"  "online-prev" "online" "updated"                           "updated-by"
# NE online
2023-01-31T13:02:03Z  True  True  2023-01-31T13:02:16.534Z  nuvlabox/30eb7dd1-3e14-4f13-a71c-fd47c5e8d474
2023-01-31T13:02:03Z  True  True  2023-01-31T13:03:09.633Z  nuvlabox/30eb7dd1-3e14-4f13-a71c-fd47c5e8d474
# NE goes offline as detected by job-engine
2023-01-31T13:02:03Z  True  False  2023-01-31T13:04:37.594Z  group/nuvla-admin
# NE goes online - telemetry published by NE
2023-01-31T13:02:03Z  False  True  2023-01-31T13:05:21.604Z  nuvlabox/30eb7dd1-3e14-4f13-a71c-fd47c5e8d474
# NE continues to be online (it is sending telemetry)
2023-01-31T13:05:37Z  True  True  2023-01-31T13:05:50.595Z  nuvlabox/30eb7dd1-3e14-4f13-a71c-fd47c5e8d474
2023-01-31T13:06:06Z  True  True  2023-01-31T13:06:19.497Z  nuvlabox/30eb7dd1-3e14-4f13-a71c-fd47c5e8d474
2023-01-31T13:06:35Z  True  True  2023-01-31T13:06:48.755Z  nuvlabox/30eb7dd1-3e14-4f13-a71c-fd47c5e8d474
2023-01-31T13:07:04Z  True  True  2023-01-31T13:07:17.640Z  nuvlabox/30eb7dd1-3e14-4f13-a71c-fd47c5e8d474
# NE goes offline as detected by job-engine
2023-01-31T13:07:04Z  True  False  2023-01-31T13:08:38.026Z  group/nuvla-admin
# >>> NE is online... but the nuvlabox-status with "False to True" transition is missing
2023-01-31T13:08:02Z  True  True  2023-01-31T13:08:50.914Z  nuvlabox/30eb7dd1-3e14-4f13-a71c-fd47c5e8d474
2023-01-31T13:09:06Z  True  True  2023-01-31T13:09:20.854Z  nuvlabox/30eb7dd1-3e14-4f13-a71c-fd47c5e8d474

In the case of # >>> NE is online... but the nuvlabox-status with "False to True" transition is missing user doesn't get the online notification and when the next time job-engine detects NE is offline user receives the offline notification.

So, instead, the new implementation should rely purely on the online flag transitions. This will require a memory that is shared across the scaled instances of the service.