Is x-v header mandatory or optional?

Question

WIth reference to CDS v1.17.0, for some Register APIs, the x-v header is optional, but for other APIs it is mandatory. Is the x-v header mandatory or optional?

Answer

On the initial implementation of older Register APIs, the x-v header was not included. Many Data Holders (DHs) have implemented to that spec. In CDS v1.17.0, for new variants of the existing APIs, the x-v header is mandatory. In future the x-v header will be mandatory as for all other CDR resource APIs.