Description of feature request

Currently, when there are no included resources, there is no included key. However, as of JSON API 1.1 this is required and in older versions it is certainly allowed. So whenever a user has requested includes with the query parameter include an included key needs to be part of the result. But only then. If there is no include query parameter, no include should be added.

Checklist

• Raised initially as discussion Adding support for JSON:API v1.1 #1092
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where feasible.)
• I have reduced the issue to the simplest possible case.