Consider adding observeaction operations

[benfrancis]

Currently it's possible to observe properties and subscribe to events, but the status of an action has to be polled with a queryaction operation. It would be more efficient in many protocols (e.g. HTTP using Server-Sent Events) to "observe" an action so that status changes are pushed to the Consumer.

Potential new operation types:

• observeaction
• unobserveaction
• observeallactions
• unobserveallactions
• observemultipleactions
• unobservemultipleactions

[egekorkan]

In principle, I agree with the different semantics of these different operations. The one issue I have is that we will have way too many operations and it will be difficult for readers to keep track of them.

[lu-zero]

#1692 is the original discussion about it.

[benfrancis]

Thanks, closing as duplicate of #1692.