Multiple `Vary` headers do not get combined in their cache key

[Xaroth]

Hi,

I'm talking against a REST API that returns Multiple Vary headers; when inspecting the cached data, I only see the first header picked up in the cache key.

The headers I see are as follows:

Vary: Accept-Language
Vary: X-Compatibility-Date

Yielding the following cache key:

[{"id":"https://esi.evetech.net/status#4784471511142272886","vary":"Accept-Language","vary_resolved":{"Accept-Language":""},"received_at":"2026-02-05T01:19:47Z"}]

In this case, changing the X-Compatibility-Date request header value does not change the cache key, resulting in possibly the wrong cache data being returned.