Response code for stale published value or empty response, "no content"

[mjkoster]

Currently we define a "no content" response, such as when a GET is done on a value which has expired its lifetime, with 2.04. We should probably define a new response code like 2.06 for this instead of trying to overload the 2.04 when used as a "changed" response to POST or PUT.

[mjkoster]

The semantic of this code is not the same as the HTTP 204 "No Response". 204 indicates that the data have not changes and the client may continue to use the last transmitted value. We need a response code that indicates data are not transmitted because of staleness and the client should not use the last transmitted value.

[mjkoster]

Suggest we create an equivalent response code to HTTP 202 Accepted

202 Accepted
The request has been accepted for processing, but the processing has not been completed. The request might or might not be eventually acted upon, and may be disallowed when processing occurs.

Suggest using 2.07