Add support for devfile 2.0 global variables

[amisevsk]

What does this PR do?

Add support for devfile 2.0 variables. In most string fields in a DevWorkspace, DWO will attempt to replace the string {{ some-variable }} with the corresponding variable from .spec.template.variables.

If a replacement cannot be found, a new condition DevWorkspaceWarning is set on the DevWorkspace with a message like

Error processing variable replacements: invalid variables in component test-container: 'test-variable'"

and the info message will be updated to include some warning text, e.g.

NAME         DEVWORKSPACE ID             PHASE      INFO
theia-next   workspace89e5bf5e04b34b6b   Starting   [warnings present] Waiting for workspace deployment

What issues does this PR fix or reference?

#508

Is it tested? How?

Apply the DevWorkspace below:

cat <<EOF | kubectl apply -f -
kind: DevWorkspace
apiVersion: workspace.devfile.io/v1alpha2
metadata:
  name: theia-next
spec:
  started: true
  template:
    attributes:
      controller.devfile.io/storage-type: "ephemeral"
    variables:
      test-variable: "testing_value"
    components:
      - name: test-container
        container:
          image: quay.io/libpod/busybox:latest
          command: ["tail"]
          args: ["-f", "/dev/null"]
          env:
          - name: TEST_ENV
            value: "{{test-variable}}"
      - name: theia
        plugin:
          uri: https://che-plugin-registry-main.surge.sh/v3/plugins/eclipse/che-theia/next/devfile.yaml
EOF

The value in the env var should be replaced once the pod is created.

To test warnings, delete the variable from the devworkspace

PR Checklist

• E2E tests pass (when PR is ready, comment /test v7-devworkspaces-operator-e2e, v7-devworkspace-happy-path to trigger)
  • v7-devworkspaces-operator-e2e: DevWorkspace e2e test
  • v7-devworkspace-happy-path: DevWorkspace e2e test

[JPinkney]

Just tested and it LGTM

[sleshchenko]

I just tested and works as expected. Please create an issue for dashboard to take into account DevWorkspaceWarning.

[sleshchenko]

when I tested I noticed that probably there are even more quotas than we would like to have

  conditions:
  - lastTransitionTime: "2021-07-28T12:57:33Z"
    message: 'Error processing variable replacements: invalid variables in component
      vsix-installer: ''test-variable''; invalid variables in component tools: ''test-variable'''

Ah, I see. It's ' is used for multilines, and '' is escaped '

[amisevsk]

The joys of YAML :D

For a while I wanted to use %q instead of %s (so that it would print "var" instead of print var), but that ends up requiring escapes all the time.

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: amisevsk, JPinkney, sleshchenko

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[amisevsk]

Created dashboard issue: eclipse-che/che#20220

[openshift-ci]

New changes are detected. LGTM label has been removed.

[amisevsk]

/test v7-devworkspaces-operator-e2e, v7-devworkspace-happy-path