Generate job UUID in start-proxy action

[mbg]

The start-proxy action precedes the init action in Default Setup, but a UUID for the analysis is only generated in the init action. That means that telemetry from the start-proxy step is not easy to associate with subsequent steps in the workflow.

This PR refactors the existing code that's duplicated across init and setup-codeql into a function, allows it to retrieve the existing job UUID from the environment, adds tests, and then uses the new function in start-proxy. This ensures that telemetry from start-proxy includes a unique identifier and the same one is used for the rest of the workflow, while workflows that don't use start-proxy also still generate one in init.

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Which use cases does this change impact?

Workflow types:

• Advanced setup - Impacts users who have custom CodeQL workflows.
• Managed - Impacts users with dynamic workflows (Default Setup, Code Quality, ...).

Products:

• Code Scanning - The changes impact analyses when analysis-kinds: code-scanning.
• Code Quality - The changes impact analyses when analysis-kinds: code-quality.
• Other first-party - The changes impact other first-party analyses.

Environments:

• Dotcom - Impacts CodeQL workflows on github.com and/or GitHub Enterprise Cloud with Data Residency.
• GHES - Impacts CodeQL workflows on GitHub Enterprise Server.

How did/will you validate this change?

• Unit tests - I am depending on unit test coverage (i.e. tests in .test.ts files).
• End-to-end tests - I am depending on PR checks (i.e. tests in pr-checks).

If something goes wrong after this change is released, what are the mitigation and rollback strategies?

• Rollback - Change can only be disabled by rolling back the release or releasing a new version with a fix.

How will you know if something goes wrong after this change is released?

• Telemetry - I rely on existing telemetry or have made changes to the telemetry.
  • Dashboards - I will watch relevant dashboards for issues after the release. Consider whether this requires this change to be released at a particular time rather than as part of a regular release.
  • Alerts - New or existing monitors will trip if something goes wrong with this change.

Are there any special considerations for merging or releasing this change?

• No special considerations - This change can be merged at any time.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.

[mario-campos]

One nit but otherwise makes sense and LGTM.

[henrymercer]

Perhaps it would make sense to do this in createStatusReportBase so we don't have to remember to call this in every Action that might run as the first step.

[mbg]

I was actually thinking about putting it in runInActions since that's intended to be the common entry point for all actions, but that would mean some more work to make that suitable for all actions.

[henrymercer]

This seems like it could be surprising — it'll silently discard all env var writes, while getTestEnv preserves writes.

[mbg]

Yeah, I agree. I cherry-picked this from a different branch where I was working on adding exportVariable to ActionsEnv and had stalled on what I wanted the test behaviour of exportVariable to be there. I'll have a go at improving this.

[mbg]

I have pushed a few commits which make the test ActionsEnv backed by an Env and then added a way of asserting that the Env contains particular entries after the main assertion has run.