Hi,

these two patches add couchdb. First, an upgrade to erlang is essential, since
our version is quite outdated and has known issues with couchdb. I’m only
bumping to a newer maintenance release of 21.x for now. `guix refresh
--list-dependent` lists only elixir, which builds fine with the new version and
emacs-erlang, build from the same sources, seems to work too.

The second patch adds couchdb. I’ve got almost the entire test suite up and
running. It is very extensive and takes a lot of time (compared to
compilation). Some patching is required to unbundle Erlangs ERTS, so an update
to Erlang in the future might break 'install due to the hard-coded version. Any
thoughts?

Future work: Shepherd service.

Cheers,
Lars