Delivering of ChePlugins binaries to the editor container

[garagatyi]

Description

Walking skeleton epic describes that we need an ability to deliver ChePlugins binaries to a che editor sidecar container. This would allow us, for example, to have a dynamic pluggability in Che Theia.
There might be different ways to deliver those binaries, so we need to investigate options and implement at least one of them for the walking skeleton POC.
Delivering options:

1. Usage of data containers that don't run any process but pulled from a registry and mount some folder to another container (editor container)
2. Download binaries from a marketplace (for now it is just an Apache server)
3. Usage of init container in kubernetes

We might also think about ChePlugins owners being able to use different mechanisms (described here or others) depending on their needs but this is not needed for a POC and it might complicate the flow, so having just one mechanism seems more natural for me for the time being.

Subtasks:

• Investigate delivering of Theia plugins with data containers Investigate delivering of Theia plugins with data containers #10369
• Add a plugin downloader component in wsmaster that
  • Get as input the workspace config list of plugins and editor
  • Downloads the plugins and editor files (*.tar.gz and *.theia) from the plugin registry
  • Extract the tar.gz in che-plugins and che-editor folders
  • Copies *.theia files in a theia-plugins folder
  • Returns the local paths to the che-plugin.yml and che-editor.yml files
• Add an editor plugin injector component in wsmaster that copies the content of editor plugins folder (theia-plugins) in the volume that will be mounted in the theia container

[l0rd]

I have created this document to discuss this issue implentation and introduce the concept of Che Plugin Broker.

[garagatyi]

Work was done in a branch but there were technical difficulties.
The plan is to:

• clean up the code from the mentioned branch and update PR Move WS.NEXT flow to k8s infra implementation, rework it to use plugin broker #10740
• work on fixes of hardcoded workarounds in separate PRs