When 'versions' is empty, the « From an existing version » option in
the template is hidden. However reversed() returns an iterator, which
is never False -> need to coerce versions into a list.

close #249

- add config key ALLGO_WEBAPP_DEFAULT_MEMORY_LIMIT_MB to set the
  default memory limit for newly created webapps

- add memory limit field in WebappUpdate

- display memory_limit in megabytes in the UI (through the
  memory_limit_mb form field)

- disable the memory_limit_mb widget and ignored the posted value
  when user is not superuser

- forbid negative value in the model

- make the memory limit field required in the forms

close #272

close #269, #270

Note: checking os.path.exists(job.data_dir) is no longer required
      since the data dir is always created (even if the job has
      no input files)

- fix url conflict for .zip archive download
- fix empty zip file

close #268

(was not used at all)

because django sets a foreign key constraint on sandbox_version_id
we may have issues if it refers to a version we want to delete

With this change docker images are no longer
named as: <Webapp.docker_name>:<WebappVersion.number>
but       <Webapp.docker_name>:id</WebappVersion.id>

This is only for storage, for the user we still present the image as
<Webapp.docker_name>:<WebappVersion.number>

There are multiple reasons to do that:
- this simplifies the controller design, because docker images are no
  longer replaced (once an image is committed with tag, 'id<SOMETHING>'
  it won't be modified anymore) -> thus it is no longer necessary to
  track the image state carefully (when pushing/pulling from/to the
  registry)
- this prevent reusing dangling images from a removed webapp (because we
  now have a strong guarantee that the image tags are unique)
- this will avoid nasty race conditions when we implement direct 'push'
  to the registry (because we then assign the new image id before the
  manifest is actually pushed, if a push and commit are done in the same
  time we will keep the latest one, i.e. with the highest id)
- this will make easy to implement image recovery: we can keep removed
  images in the registry for some time (eg: 1 month) before they are
  really deleted

Note: the REPLACED state is no longer transient (since we now keep the
replaced images in the db and since we may still have remaining
job/sandboxes using them). Maybe we can rename it as DELETED when we
implement #265.

I updated the tag views by importing the `Tag` model provided by the
Taggit plugin, deleted the `WebappTag` model and `TagForm` form that are
obsolete.
I updated the `WebappUpdate` view to follow the recommendation given by
the Taggit plugin documentation. The `TagList` now uses directly the
`Tag` model and send both the tag fields and a count of each tag
occurence.
I removed the `TagAdd` list that is obsolete. I updated the
`TagWebappList` that returns simply a list of all `Webapp`objects for a
given tag.
Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>

Follwoing the merge, several bugs appeared. I added the import of the
`transaction` Django library and `get_base_url` missing function calls.
I updated as well the sandbox panel handle in the template because it
changed with the merge.
Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>

This way we get redis updates when a job is deleted and this also
prevents inserting a 'DONE' state when the job is not done

Note: we never update the redis job state key from the django server to
avoid race conditions

This updates the job_list page in real time when the state of any
displayed job changes:
- update the status icon
- show/hide the abort button
- enable/disable the delete button
- remove job from the list when destroyed

(also changed the status_icon to fa-hand-paper which looks
 (i think ;-) less confusing)

close #222

(from the user point of view, these jobs no longer exist)

The controller and django can both change the job state, especially when
it is in the WAITING state (django may delete the job and the controller
may start the job).

To prevent any inconsistency, we must ensure that these transitions are
made atomically.

(because the controller must free the allocated resources first)

(chromium does support empty "Location:" header)

- form reformatted as a grid (using class form-row)
- when replacing a version
  - select the version used for starting the current sandbox
  - initialise the "changelog" field with the previous changelog
    of the version being replaced
- when creating a new version
  - initialise the "changelog" field with an empty value
  - raise an error if the entered version already exists
    (prevents accidental overwriting by the user)
- report commit result in a flash message

BERJON Matthieu authored Jul 25, 2018 and BAIRE Anthony committed Aug 01, 2018

The redirection for a successful webapp creation was wrong and created
an error. I fixed it by giving te right handle (i.e
`webapp_sandox_panel`).
Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>

- all sandbox actions a made from the same endpoint, so i renamed it as
  WebappSandboxPanel. It is an endpoint that accept GET and POST methods
- GET is rendered using TemplateView (nothing magic)
- POST is has an ad-hoc implementation that handles sandbox
  actions (start, commit, rollback, retry, abort)
- all POST actions are followed with an HTTP redirect (to make a GET)
  so that actions are repeated if the user refresh his browser window
- I changed the initial status of newly created webapps to IDLE because
  power users who upload their docker image do not need to start a
  sandbox

It is not finished, there are many FIXMEs/TODOs but it is working.

instead of '1' (which will mostlay always be wrong)

This is to avoid code duplication (the kind of nasty duplication
where is damn easy to forget to update both sides). Plus the converter
ensures the arguments are properly shell-escaped using shlex.quote().

This also fixes the resolution of the port when it is provided in the
X-Forwarded-Host header.

It is a good practice to authenticate before, because this prevents
leaking information.

(also i removed the json error messages because they are ignored by
 nginx, if we want to tune them, then we should do it in the nginx
 configuration)

(must return 401 instead)

I fixed the bug in two `DeleteView` views. The `SuccessMessageMixin`
doesn't work with `DeleteView` views because it's hooked to the
`form_valid` method which doesn't exist in this particular view.

I took the opportunity to rewrite the other success or error messages in
the other views in order to have something a bit clearer and easier to
read.
Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>