Add support for activity pause

[Quinn-With-Two-Ns]

closes #2465

[cretz]

Nothing blockling

[cretz]

Hrmm, so I see this is in the client package. I am guessing some other extensions of this activity completion exception are in client package instead of the activity one because they can be the cause of the outer activity failure when caught inside a workflow, correct? My concern with this exception is that it is only for inside activities and never for inside workflows.

Not that it's wrong or anything, but I wonder if it's worth noting in javadoc that even if, say, max attempts were reached as a result of this being bubbled out of the activity, the workflow caller will never see this exception.

[Quinn-With-Two-Ns]

All other ActivityCompletionException are in client , I agree it is not the ideal package but it is consistent with the rest of the SDK.

the workflow caller will never see this exception.

That is just the basic failure conversion rules for activities https://docs.temporal.io/references/failures#errors-in-activities I don't think we should document it for every SDK exception.