Merge queue stats metrics and dashboard in Datadog

Version 2.0.0 of the Mergify integration for Datadog goes much deeper on merge queue monitoring. It adds 19 mergify.queue.* metrics covering throughput (pull requests entered and merged, queue and batch size), queue health (exit reasons, check outcomes, CI retries, bisections), and performance (time in queue, CI runtime, idle waits), all tagged by repository, branch, queue, and priority_rule. The integration also bundles an out-of-the-box Mergify - Merge Queue Stats dashboard, ready to use as soon as metrics flow in.

The legacy metrics (mergify.merge_queue_length, mergify.time_to_merge.*, mergify.queue_checks_outcome) are deprecated in favor of the new mergify.queue.* metrics.

Enable the integration from your Mergify dashboard — see the Datadog integration docs.