In some cases proxy should sanitize incoming headers. --drop-header and $DROP_HEADERS set list of headers (keys) and those headers removed from the request.
* wip
* resolve merge artifacts
* full coverage for conductor
* wire plugin conductor to main and proxy
* wip, with separate match handler
* split matching logic with another handler, add initial docs
* move parts of proxy to handlers, add tests
* add headers in to be sent to proxied url
* merged from master
* add example with docker compose
* supress excesive debug reporting 0-9 disabled in docker
* add plugin tests
* randomize test port
* lint: minor warns
* lint: err shadow
