build: Add Konflux pipeline activation through a label

[msugakov]

Once PR is created with some branch name, it may be handy to enable Konflux builds on demand.

Inspiration from https://pipelinesascode.com/docs/guide/authoringprs/#using-the-body-and-headers-in-a-pipelines-as-code-parameter and https://github.com/google/cel-spec/blob/master/doc/langdef.md#list-of-standard-definitions.

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[msugakov]

Figured (#1594) that body.pull_request.labels look the following way:

    "labels": [
      {
        "color": "ededed",
        "default": false,
        "id": 4164972636,
        "name": "do-not-merge/work-in-progress",
        "node_id": "LA_kwDODLkO9s74QHBc",
        "url": "https://api.github.com/repos/stackrox/scanner/labels/do-not-merge/work-in-progress"
      },
      {
        "color": "D55C85",
        "default": false,
        "description": "Tells (Konflux) Renovate bot to calm down and not send more updates to this PR.",
        "id": 6987805440,
        "name": "stop-updating",
        "node_id": "LA_kwDODLkO9s8AAAABoIFzAA",
        "url": "https://api.github.com/repos/stackrox/scanner/labels/stop-updating"
      },
      {
        "color": "B0FE49",
        "default": false,
        "description": "Enable Konflux builds in this PR",
        "id": 7304553284,
        "name": "konflux-build",
        "node_id": "LA_kwDODLkO9s8AAAABs2KjRA",
        "url": "https://api.github.com/repos/stackrox/scanner/labels/konflux-build"
      }
    ],

[tommartensen]

Is the pipeline also triggered when you add or remove the label? From what I can see in the history of this PR, you added the label, then pushed 53b0dcc, for which Konflux started to run.

[msugakov]

The pipeline does not start after I just add the label. Something needs to be committed to the PR branch. This works similar to our existing labels in stackrox project.

[tommartensen]

The pipeline does not start after I just add the label. Something needs to be committed to the PR branch. This works similar to our existing labels in stackrox project.

GHA and OSCI can be triggered just by adding the label, e.g. backport release-4.5 labels work like that.
might be a question for #konflux-users.

[msugakov]

Following up here https://redhat-internal.slack.com/archives/C05TS9N0S7L/p1723107909357619

[msugakov]

/test scanner-db-slim-build