if box code restarts in the middle of a apptask, the onFinished handlers
are not called for data migration and update. rework the code to hook
the onFinished handlers when the task completes and not where the task
is started.
There are two main use cases:
* A consultant/contractor/external developer is given access to just an app.
* A "service" personnel (say upstream app author) is to be given access to single app
for debugging.
Since, this is an "app admin", they are also given access to apps to be consistent with
the idea that Cloudron admin has access to all apps.
part of #791
this tries to solve two issues:
* the current approach mounts the data directories of apps/volumes individually.
this causes a problem with volume mounts that mount after the container is started i.e not
network time/delay but systemd ordering. With CIFS, the mount is a hostname. This requires
unbound to be running but unbound can only start after docker because it wants to bind to
the docker network. one way to fix is to not start sftp automatically and only start sftp
container in the box code. This results in the sftp container attaching itself of the
directory before mounting and it appears empty. (on the host, the directory will appear
to have mount data!)
* every time apptask runs we keep rebuilding this sftp container. this results in much race.
the fix is: mount the parent directory of apps and volumes. in addition, then any specialized appdata
paths and volume paths are mounted individually. this greatly minimized rebuilding and also since we don't rely
on binding to the mount point itself. the child directories can mount in leisure. this limits the race
issue to only no-op volume mounts.
part of #789
clone also clones the tags, labels and icon. this is not done for
restore or import since it's not clear if this is a good idea or not.
for example, if user had some custom tags and label set and then restores
to some old backup, is it expected to reset the labels and tags?
the notification wasn't working because this was in apptask and the apptask died
before it could send out the email. we now move the notification to box process
and also remove the email notification.
