When an HTTP/2 request which multiple cookie headers is send to Undertow, the following happens:
- The HTTPServertExchange has all cookies
- The HTTPServletRequest has all cookies
- The multiple cookie headers are NOT combined into a single cookie header again per the spec
This breaks applications who do their own parsing of the cookie header and only grab the first (or last) cookie header as they will only "see" one cookie. It is forbidden to have more than one cookie header in HTTP/1.
Undertow needs to correctly reassemble multiple cookie headers from HTTP/2 requests into a single header so app can properly parse the header manually.