What type of PR is this?

• documentation

What this PR does / why we need it:

The Design Guide states that the DeviceResponse schema should be used to disambiguate which device identifier is being used by an implementation when an API consumer has provided more than one identifier, but it does not mandate it. Nor should it, as there will be APIs for which it is not appropriate. If it is used by an API, however, then it becomes mandatory to provide a single device identifier in the response when multiple are provided in the response.

This PR clarifies that:

• The DeviceResponse schema is not mandatory for an API
• If used in a response definition, however, the API provider:
  • MUST include in the response which device identifier is being used when multiple have been provided
  • MAY always include the device identifier in the response even when only one has been provided

Which issue(s) this PR fixes:

Fixes #489

Does this PR introduce a breaking change?

• Yes
• No

Special notes for reviewers:

None

Changelog input

 release-note
 - Clarify that the DeviceResponse schema is not mandatory

Additional documentation

None