We have graduated twenty-three of the twenty-five existing previews that were in our REST API.
Previously, REST API consumers needed to pass in a custom media-type via an HTTP accept header (example:
Accept: application/vnd.github.ant-man-preview+json) with requests to get additional response fields or to be able to access specific endpoints.
The following are REST APIs that still require the accept header:
content_references (corsair preview)
code_of_conduct (scarlet-witch preview)
The header is no longer needed for the other twenty-three REST API previews that have been graduated.
For the remaining two previews the plan is to sunset the previews later this year. We are actively reaching out to any consumers of the REST APIs of those previews.