Support Singlehost deployment in Devworkspaces

[metlos]

Is your task related to a problem? Please describe.

Currently, devworkspace operator always uses ingresses to expose workspace endpoints (similar to the multi-host mode in Che).

It would be great to make it also support an analog of the singlehost mode of Che.

Describe the solution you'd like

It would be great if we could implement this as a separate controller out of the main devworkspace-operator. This would enable us to keep the main operator focused on the workspace lifecycle management and the concerns like workspace exposure would be delegated to other, potentially external, controllers.

The devworkspace operator already has a concept of WorkspaceRouting expressed as a standalone CR that is used to handle the different ways a workspace is exposed and already handles a couple such exposure types (openshift-oauth, web-terminal, basic, ...). We could take advantage of this concept and implement singlehost as a new type of workspace routing.

Describe alternatives you've considered

We could implement this inside devworkspace operator itself as a new workspace routing solver. This would require deploying other components (if we copy the singlehost approach taken by Che, that would mean deploying Traefik from within the operator).

Additional context

This depends on devfile/devworkspace-operator#219

Subtasks:

• [devworkspace] Manage Traefik as the devworkspace gateway [devworkspace] Manage Traefik as the devworkspace gateway #18677
• [devworkspace] Implement singlehost workspace routing solver for devworkspaces [devworkspace] Implement singlehost workspace routing solver for devworkspaces #18678

[amisevsk]

I set P2 on this one since it's still outside of the main flow; feel free to increase if appropriate.

[metlos]

The code for this now lives in https://github.com/che-incubator/devworkspace-che-operator