Previously, we would reject this with a 400 error. Considering the
request body is expected to contain "array of requests" and that arrays
may be empty, we really should not be rejecting the requests.
Prior to 156ca21472, sending the empty array would have been convenient
for channel creation. Empty arrays getting rejected forced clients to
inject a faux poke (commonly hi-ing oneself). With that recent change,
the most common case for wanting to PUT the empty list of requests is
largely obsolete, but one can still imagine it being useful for clients
that want to keep their channel alive without necessarily being
connected to it. This also implements sloppier clients from running into
400 responses when they submit an empty "command queue" for whatever.
Regardless, there seems to be no clear reason why the empty request list
_shouldn't_ be accepted and processed as normal.
We add a small test to ensure eyre accepts this.
Previously, a channel could only be created by sending a PUT request,
and a GET request to receive the channel's stream would only succeed
after channel creation had happened that way. This forces client
libraries, that generally have an explicit "set up" step before allowing
normal operation, to do strange things, like sending faux pokes
(commonly hi-ing oneself) before connecting to the channel's stream as
normal.
Here, we update the GET request handling for channels to allow requests
for non-existent channels. When this happens, the channel will be
created, and eyre tracks the request as normal.
We do some... gentle restructuring... of +on-get-request:by-channel to
let the new creation case share code with the "already exists" codepath.
In the process, we find that duct-to-key was never getting updated in
the case where we replace the original channel request/connection with
the new incoming one. We fix this, it's trivial. We also identify two
other areas with vaguely-incorrect behavior, but consider them less
important and out of scope.
We also add a test case for "create channel through GET".
