Repo Gardening: log failures to send Slack messages

Fixes #40366

Until now, we used to try to send messages to Slack, and didn't do anything if the message could not be sent. We'll now log the message, either by sending a Slack message to myself, or the Quality team for folks outside of the Automattic organization.

This will allow us to better detect triage Slack actions that could not be completed, because a team no longer exists and their Slack channel has been archived for example.

projects/github-actions/repo-gardening/changelog/update-repo-gardening-slack-report-message

@@ -0,0 +1,4 @@
+Significance: patch
+Type: changed
+
+Slack messaging: when a Slack message cannot be sent to a specific channel, send a message to warn about the issue.

projects/github-actions/repo-gardening/src/utils/slack/send-slack-message.js

@@ -88,6 +88,68 @@ async function sendSlackMessage( message, channel, payload, customMessageFormat
 		},
 	} );
 
+	// If the request failed, let's send a direct message to @jeherve about it, so we can investigate.
+	// For folks outside of Automattic, let's use the Quality team channel.
+	if ( ! slackRequest.ok ) {
+		const {
+			repository: { owner },
+		} = payload;
+		const { html_url, title } = payload?.pull_request ?? payload.issue;
+
+		const reportingChannel =
+			owner === 'automattic' ? 'D1KN8VCCA' : getInput( 'slack_quality_channel' );
+		if ( ! reportingChannel ) {
+			return false;
+		}
+		const reportMessage = {
+			channel: reportingChannel,
+			blocks: [
+				{
+					type: 'section',
+					text: {
+						type: 'mrkdwn',
+						text: `Error sending message to Slack: ${ slackRequest.error }`,
+					},
+				},
+				{
+					type: 'divider',
+				},
+				{
+					type: 'section',
+					text: {
+						type: 'mrkdwn',
+						text: `<${ html_url }|${ title }>`,
+					},
+					accessory: {
+						type: 'button',
+						text: {
+							type: 'plain_text',
+							text: 'Review',
+							emoji: true,
+						},
+						value: 'click_review',
+						url: `${ html_url }`,
+						action_id: 'button-action',
+					},
+				},
+			],
+			text: `Error sending message to Slack: -- <${ html_url }|${ title }>`, // Fallback text for display in notifications.
+			mrkdwn: true, // Formatting of the fallback text.
+			unfurl_links: false,
+			unfurl_media: false,
+		};
+		await fetch( 'https://slack.com/api/chat.postMessage', {
+			method: 'POST',
+			body: JSON.stringify( reportMessage ),
+			headers: {
+				'Content-Type': 'application/json; charset=utf-8',
+				'Content-Length': reportMessage.length,
+				Authorization: `Bearer ${ token }`,
+				Accept: 'application/json',
+			},
+		} );
+	}
+
 	return !! slackRequest.ok;
 }