feat(web): add automatic actions for open pull requests

A new pr_open alert carries the head commit SHA of each open, non-draft, same-repository pull request. An action with auto enabled sends its webhook once for each pull request and head commit. An authors list limits which pull requests trigger it. The alert never changes repository health.

internal/collector/health.go

@@ -20,6 +20,8 @@ const (
 	KindPRWaiting     = "pr_waiting"
 	KindPRChecks      = "pr_checks_failing"
 	KindIssuesStale   = "issues_stale"
+	// KindPROpen is informational plumbing for automatic actions; it has OK severity so it never moves health or counts.
+	KindPROpen = "pr_open"
 )
 
 // Evaluate derives alerts for one repo at time now and stores the worst severity in r.Health.
@@ -62,6 +64,10 @@ func Evaluate(r *model.Repo, now time.Time, th config.Thresholds) []model.Alert
 		}
 		age := now.Sub(pr.CreatedAt)
 		subject := fmt.Sprintf("#%d %s", pr.Number, pr.Title)
+		if !pr.Fork {
+			alerts = append(alerts, model.Alert{Severity: model.OK, Repo: r.FullName, Kind: KindPROpen, Subject: subject,
+				Detail: "open for " + Age(age), URL: pr.URL, Ref: pr.HeadSHA, Author: pr.Author, Since: pr.CreatedAt})
+		}
 		switch {
 		case th.PRCritAfter > 0 && age >= th.PRCritAfter:
 			add(model.Crit, KindPRWaiting, subject, "open "+Age(age), pr.URL, pr.CreatedAt)