Low-level configuration support for onion services
We'll need code in tor-hsservice to handle the configuration of a single onion service. This should only include the parts that tor-hsservice needs to do itself, and not things like key managers and state managers that are handled by other code that calls into tor-hsservice. Some of the possible values that might go here are outlined in doc/dev/notes/onion-service-notes.md
Part of #698 (closed)