Add chatterbox Slack notifications for failed PR lint runs

[jencarlucci]

This PR adds CI alerting so the API team gets notified when lint fails on pull requests.

I'll need to test this workflow once it's merged since we don't currently have a way to manually trigger the entire process.

[Copilot]

Pull request overview

Adds CI alerting so the API team is notified in #api-platform when PR lint runs fail.

Changes:

• Trigger the linter workflow on pull_request events.
• Add a workflow_run-based notifier workflow that posts failures to chatterbox/Slack.
• Document required repository secrets and workflow location in CONTRIBUTING.md.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
descriptions-next/lint-failure-test.yaml	Adds a file intended to force lint failure (used to test notifications).
CONTRIBUTING.md	Documents CI notification behavior and required secrets.
.github/workflows/linter.yml	Enables lint workflow on PRs in addition to pushes.
.github/workflows/linter-failure-notifier.yml	New workflow to post chatterbox notifications on failed PR lint runs.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

This file is syntactically invalid YAML and will cause lint/CI to fail continuously once merged (not just during testing). If the goal is to test notifications, consider removing this file before merge, or move it into a test/fixture location that is excluded from the linter inputs (or gate it behind a dedicated test-only workflow).

Suggested change

	trigger: [this is intentionally broken
	trigger: ["this is intentionally broken"]

[Copilot]

In bash, \"\\n\" inside double quotes is not converted to a newline; it becomes a literal backslash+n. This will post \\n sequences rather than multi-line text. Build message using actual newlines (e.g., a heredoc or printf) and consider --data-binary to preserve newline formatting in the request body.

Suggested change

	message=":warning: Linter workflow failed for a pull request in ${REPO}.\n• Workflow: ${RUN_NAME}\n• PR: ${PR_URL}\n• Branch: ${BRANCH}\n• Commit: ${short_sha}\n• Run: ${RUN_URL}"
	curl --fail --silent --show-error \
	-X POST \
	-u "${CHATTERBOX_TOKEN}:" \
	"${CHATTERBOX_URL%/}/topics/%23api-platform" \
	--data "$message"
	printf -v message ':warning: Linter workflow failed for a pull request in %s.\n• Workflow: %s\n• PR: %s\n• Branch: %s\n• Commit: %s\n• Run: %s' "$REPO" "$RUN_NAME" "$PR_URL" "$BRANCH" "$short_sha" "$RUN_URL"
	curl --fail --silent --show-error \
	-X POST \
	-u "${CHATTERBOX_TOKEN}:" \
	"${CHATTERBOX_URL%/}/topics/%23api-platform" \
	--data-binary "$message"

[Copilot]

In bash, \"\\n\" inside double quotes is not converted to a newline; it becomes a literal backslash+n. This will post \\n sequences rather than multi-line text. Build message using actual newlines (e.g., a heredoc or printf) and consider --data-binary to preserve newline formatting in the request body.

Suggested change

	message=":warning: Linter workflow failed for a pull request in ${REPO}.\n• Workflow: ${RUN_NAME}\n• PR: ${PR_URL}\n• Branch: ${BRANCH}\n• Commit: ${short_sha}\n• Run: ${RUN_URL}"
	curl --fail --silent --show-error \
	-X POST \
	-u "${CHATTERBOX_TOKEN}:" \
	"${CHATTERBOX_URL%/}/topics/%23api-platform" \
	--data "$message"
	message="$(cat <<EOF
	:warning: Linter workflow failed for a pull request in ${REPO}.
	• Workflow: ${RUN_NAME}
	• PR: ${PR_URL}
	• Branch: ${BRANCH}
	• Commit: ${short_sha}
	• Run: ${RUN_URL}
	EOF
	)"
	curl --fail --silent --show-error \
	-X POST \
	-u "${CHATTERBOX_TOKEN}:" \
	"${CHATTERBOX_URL%/}/topics/%23api-platform" \
	--data-binary "$message"

[Copilot]

The workflow_run payload’s pull_requests array can be empty in some cases, which would leave PR_URL blank and degrade the alert. Add a fallback (e.g., link to RUN_URL, or query the PR via the GitHub API using head_sha when pull_requests[0] is missing).