Problem description
In our subscription model we offer possibility for server to handle it synchronously or asynchronously.

Suppose we have a subscription request that the server is not able to handle (the monitoring area is not within operator area, the reachability status could ne follow this specific number, etc...) and the subscription server handles it in async mode.

How to inform the subscription requester that the request in not processable when server manages it in asynchronously ?

(in sync mode we do not have issue as we send back a 4xx error)

Possible evolution

• add another TerminationReason value: SUBSCRIPTION_UNPROCESSABLE
• add terminationReasonComment attibute to allow server to provide explantation

Alternative solution

Additional context
cc: @PedroDiez & @shilpa-padgaonkar @akoshunyadi