feat: add initial scheduled task implementation

This functionality enables users to manage a global crontab for the Dokku user that contains all scheduled tasks across all apps. Alternative schedulers can implement cron tasks as desired.

plugins/cron/src/triggers/triggers.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/dokku/dokku/plugins/common"
+	cron "github.com/dokku/dokku/plugins/cron"
+)
+
+// main entrypoint to all triggers
+func main() {
+	parts := strings.Split(os.Args[0], "/")
+	trigger := parts[len(parts)-1]
+	flag.Parse()
+
+	var err error
+	switch trigger {
+	case "post-delete":
+		err = cron.TriggerPostDelete()
+	case "post-deploy":
+		err = cron.TriggerPostDeploy()
+	case "report":
+		appName := flag.Arg(0)
+		err = cron.ReportSingleApp(appName, "")
+	default:
+		common.LogFail(fmt.Sprintf("Invalid plugin trigger call: %s", trigger))
+	}
+
+	if err != nil {
+		common.LogFail(err.Error())
+	}
+}