Now that our image tarball is not tagged as 'latest', we must first grab
the image tag first, and then refer to it. We can grab the tag either
from `share/image-id.txt` (if available) or with:
docker load dangerzone.rocks/dangerzone --format {{ .Tag }}
Add the following two methods in the isolation provider:
1. `.is_available()`: Mainly used for the Container isolation provider,
it specifies whether the container runtime is up and running. May be
used in the future by other similar providers.
2. `.should_wait_install()`: Whether the isolation provider takes a
while to be installed. Should be `True` only for the Container
isolation provider, for the time being.
Revamp the container image installation process in a way that does not
involve using image IDs. We don't want to rely on image IDs anymore,
since they are brittle (see
https://github.com/freedomofpress/dangerzone/issues/933). Instead, we
use image tags, as provided in the `image-id.txt` file. This allows us
to check fast if an image is up to date, and we no longer need to
maintain multiple image IDs from various container runtimes.
Refs #933
Refs #988Fixes#1020
Build Dangerzone images and tag them with a unique ID that stems from
the Git reop. Note that using tags as image IDs instead of regular image
IDs breaks the current Dangerzone expectations, but this will be
addressed in subsequent commits.
Add the following methods that allow the `Container` isolation provider
to work with tags for the Dangerzone image:
* `list_image_tag()`
* `delete_image_tag()`
* `add_image_tag()`
