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/subcommands/subcommands.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/dokku/dokku/plugins/common"
+	"github.com/dokku/dokku/plugins/cron"
+
+	flag "github.com/spf13/pflag"
+)
+
+// main entrypoint to all subcommands
+func main() {
+	parts := strings.Split(os.Args[0], "/")
+	subcommand := parts[len(parts)-1]
+
+	var err error
+	switch subcommand {
+	case "list":
+		args := flag.NewFlagSet("cron:list", flag.ExitOnError)
+		args.Parse(os.Args[2:])
+		appName := args.Arg(0)
+		err = cron.CommandList(appName)
+	case "report":
+		args := flag.NewFlagSet("cron:report", flag.ExitOnError)
+		osArgs, infoFlag, flagErr := common.ParseReportArgs("cron", os.Args[2:])
+		if flagErr == nil {
+			args.Parse(osArgs)
+			appName := args.Arg(0)
+			err = cron.CommandReport(appName, infoFlag)
+		}
+	default:
+		common.LogFail(fmt.Sprintf("Invalid plugin subcommand call: %s", subcommand))
+	}
+
+	if err != nil {
+		common.LogFail(err.Error())
+	}
+}