Incorrect use of Vary header

[paulcrussell]

Hi,

I noticed an issue on nuxt (or so I thought) initially whereby if I exclude the Accept-Encoding header completely then server assumes a plaintext response is needed but excludes the Vary header. This has the impact of poisoning the shared caches downstream with a large document without a Vary header. I.e. its going to get used for all responses.

I raised a nuxt issue but nuxt/nuxt#30857 and we decided with @danielroe it was a Nitro issue.
So I've raised #3077

I'm pretty sure the fix is to always include the Vary: Accept-Encoding and not make it dependent on the request header Accept-Encoding.

Can I raise a PR on this?

Thanks
Paul