Manager had a limit of 10 MB, but the Worker can produce images that are
larger than that (even after down-scaling the image). I've bumped the
limit to 25 MB, which should be enough (it's 2x the bug reporter's file
size).
Add a "Last Rendered" view to the webapp.
The Manager now stores (in the database) which job was the last
recipient of a rendered image, and serves that to the appropriate
OpenAPI endpoint.
A new SocketIO subscription + accompanying room makes it possible for
the web interface to receive all rendered images (if they survive the
queue, which discards images when it gets too full).
After processing an image in the "last-rendered" processor, a SocketIO
object is sent to clients to indicate the last-rendered image needs to
be (re)loaded.
This also moves the previously existing "done callback" from a single
function to a per-image callback, so that it can be called with the
right information in there, and only when that particular image is
actually done processing.
The notification message sent via SocketIO also contains the necessary
info to render the image, so that the web client doesn't have to call
the `fetchJobLastRenderedInfo` operation.
Add a handler for the OpenAPI `taskOutputProduced` operation, and an
image thumbnailing goroutine.
The queue of images to process + the function to handle queued images
is managed by `last_rendered.LastRenderedProcessor`. This queue currently
simply allows 3 requests; this should be improved such that it keeps
track of the job IDs as well, as with the current approach a spammy job
can starve the updates from a more calm job.
