[Event Service] Connect Notifications to the new Event Service

[boreq]

In order to optimize the collection of data from other relays, we want all of our internal tools to use the Event Service for retrieving event information. Assuming the Event service is performant and useful, use it to replace how Notifications currently collects events.

Notes from Filip for reference
We want to use our new event service to receive events.

Once this ticket plus the following tickets are done we can remove the code that replicates events from the notification service:

• [Event Service] Connect Notifications to the new Event Service  #47
• [Event Service] Register our users with the event service nos#663
• the app with the changes is deployed