AD flag is cached incorrectly

[ADV-R]

What happened:

It looks like if the first request does not contain AD flag, cache plugin just caches the response and responds without it even if the next requests contain such flag.

The reverse scenario when the first request contains AD flag and the next ones doesn't is working correctly.

How to reproduce it (as minimally and precisely as possible):

dig cloudflare.net +noad - no AD flag as expected
dig cloudflare.net +ad immediately after - still no AD flag when it should be here

Environment:

• the version of CoreDNS: v1.11.1