Outline a callback pattern for implementing long poll methods

Various entities provide a long poll mechanism to get changes as they occur on the server (I assume this is due to the lack of webhooks, which would be difficult to proxy in the current environment, and for clients like what we are building long poll would make sense in certain use cases).

The endpoints generally seem to return a response if there are any, otherwise return a `400` and hang up.

This ticket is to study these endpoints like `cardholder`, `alarms`, etc and determine a pattern so all of them can follow the same design principles.