Consider TLS session caching for DoH (and/or DoT)
Description
Establishing a TLS connection might be costly and involves some data exchanges that might exceed the actual DNS query size for simple queries. Haven't looked into it much, but WEB servers could do that, so should BIND.
This feature is worth at least researching because I would expect DoH clients (mostly browsers) to return shortly after making a query, so this could improve performance.