A server built with compression support compressed every handler
response the client accepted, with no way to turn it off. Over HTTPS
the length of a compressed response can give away a secret in it when
the same response also carries text an attacker chooses (BREACH).
set_compress(false) sends handler responses, buffered or streamed, as
they are; compression stays on by default, and static file compression
keeps its own setting. The README and the cookbook describe the switch
and when to use it.