Extension manager: allow manually uploading a docker image

[ES-Alexander]

Useful for installing to offline / air-gapped systems (discussed here), and for local development.

[ES-Alexander]

We'd need to add an API endpoint for loading an image (like we do in version-chooser), which then imports it into docker, before doing the normal custom extension registration process.

I propose we add a "manual upload" option to the custom registration interface for now, but once #2768 is complete there may be some other relevant interface options available too (e.g. if we want to support users installing official extension versions offline then we'd presumably want a streamlined way for them to be uploaded without needing custom registration, and possibly with key-sign verification to confirm that they're actually legit images)

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As an interim workaround it should be possible already to:

1. Upload the extension's docker image .tar ball to the BlueOS device, using either the File Browser or ssh
   • Probably makes sense to put it in the /usr/blueos/extensions folder (just extensions in the File Browser)
2. Use the BlueOS Terminal to docker import the image (may need to red-pill to be able to access the docker CLI)
3. Tag the image with a tag that doesn't exist in the online registry
   • I'm unsure whether it will already have a tag when it's imported
4. Use the custom extension registration process to register that image + tag combo

[rotu]

As an alternative to uploading a tarball, I prefer to use the docker engine on the rpi directly.

On your development machine do this once to create a context:

docker context create blueos
docker context update blueos --description "Docker Engine running on BlueOS"
docker context update blueos --docker "host=ssh://blueos.local"
docker --context=blueos buildx create --driver=docker-container --name=blueos-builder
docker --context=blueos buildx use blueos-builder --default

Switch your context (before you run docker commands) with:

docker context use blueos

Get all extension containers (i.e. name starts with extension) into a local compose file with

docker run --rm -v /var/run/docker.sock:/var/run/docker.sock ghcr.io/red5d/docker-autocompose $(docker ps -aq --filter name=extension) > compose.yaml

Remove services from that file which you don't want to edit (e.g. blueos-core).

On the service you want to edit, replace the image: ... value with build: /path/to/folder/containing/dockerfile/

Optionally, normalize your compose file with:

docker config --output compose.yaml

then edit and run with docker compose up --build