Pull request description can include external PRs

[sjohnr]

Current behavior:

When building the status_string with something like "Failed: xyz's pull_request #X from Y to Z", the description sometimes includes pull requests from external repositories (forks) that reference a particular commit. This is very surprising and makes the notification look like it's coming from someone else's fork.

Here's an example:

This was actually not a pull request at all, but a scheduled workflow. The latest commit included with the workflow run also appears in the pull requests of two separate forks that are using a pull request bot to synchronize commits with their fork, so GitHub includes them in the pull_requests field of the API. This also happens with pushes directly to a branch.

Suggested fix:

slack-workflow-status/src/main.ts

Lines 164 to 169 in de07ba9

	const pull_requests = (workflow_run.pull_requests as PullRequest[])
	.map(
	pull_request =>
	`<${workflow_run.repository.html_url}/pull/${pull_request.number}|#${pull_request.number}> from \`${pull_request.head.ref}\` to \`${pull_request.base.ref}\``
	)
	.join(', ')

These lines could filter by the owner/repo of the current workflow run to ensure this PR data is for the current repo, not a fork. In our case, this should filter out all PRs attached to this workflow, and fall back to the description of the workflow run, not a PR.