Long running operations Support

[shemogumbe]

In Azure SDK/API as an example, Long running operations are performed in the following flow?

1. A URL is returned that can be used to retrieve the result of the operation once completed.
2. The URL can be used to monitor the status of the operation, at regular intervals until it is completed.
3. Optionally a callback URL is availed that can be used to get notification once a long running operation is completed.

Technically, this looks like polling and a callback URL.

Do we have a spec on this for Graph SDKs @baywet @andrueastman @darrelmiller @ddyett @Ndiritu @samwelkanda