The `Vary` response header seems to be getting invalidated when using the HTTP Cache API

[vcarvajal-sigsci]

There appears to be a bug with regard to how the vary response header is being handled in using the http caching option. When the flag is set, --enable-http-cache, upon building the package, vary header is invalidated regardless of the use of HTTP Cache API (ie afterSend), however if the flag is not used, it works as expected.

[twhid]

@vcarvajal-sigsci Does this mean that if the --enable-http-cache is used then the vary header is ignored vis a vis caching logic within Fastly? Thanks for any clarification!