Sink credentials sent back as a part of API responses.

[shilpa-padgaonkar]

Problem description
For APIs where we have either implicit or explicit subscriptions, as a part of a successful response, we send back the sink credentials.
IMHO we should exclude this information from the response.

Expected behavior
Do not send back sink credentials as a part of the API responses.

Alternative solution

Additional context

[PedroDiez]

Related Issue Design Guidelines should provide guidance about sinkCredentials in returned/retrieved subscription objects #276

[rartych]

Let's continue discussion in

• Design Guidelines should provide guidance about sinkCredentials in returned/retrieved subscription objects #276