[OCF client] remove the update event from ClientResource.

[zolkis]

Also, change Destination.destination to Destination.endpoint.

Reason for change: when multiple endpoints are supported with a Resource, (update) event observation would need a parameter for specifying the endpoint. This is not possible with events. Hence we need to remove the convenience feature for observing resource updates with an event listener. From now on the only way to observe resource updates is by specifying a listener to the retrieve() method, i.e. follow the CoAP observe pattern (make a retrieve request with the 'observe' flag turned on).

Signed-off-by: Zoltan Kis [email protected]

[gabrielschulhof]

dictionarydestination?

[gabrielschulhof]

What happens when you want to stop observing? How do you remove the callback?

[gabrielschulhof]

I was thinking that the callback might return a special value. That's what the lower level callback does: iotivity.OCStackApplicationResult.OC_STACK_DELETE_TRANSACTION to stop and ``iotivity.OCStackApplicationResult.OC_STACK_KEEP_TRANSACTION` to keep listening.

OTOH, our high-level solution so far has been to have an entity external to the callback add/remove the callback. This would allow the callback to be free of code wherein it decides whether to stay attached or not.

[zolkis]

Based on the OCF Core spec, I expect that making a retrieve request without providing an observer (i.e. the observe flag) will stop observing.