feat: support cronjob initers

contracts/cron_job.go

@@ -1,15 +1,22 @@
 package contracts
 
 import (
-	"time"
-
 	"github.com/riverqueue/river"
 )
 
 type CronJob interface {
-	Description() string
-	Periodic() time.Duration
-	JobArgs() []river.JobArgs
-	InsertOpts() *river.InsertOpts
-	RunOnStart() bool
+	Args() []CronJobArg
+}
+
+type CronJobArgInterface interface {
+	river.JobArgs
+	river.JobArgsWithInsertOpts
+}
+
+type CronJobArg struct {
+	Kind             string
+	RunOnStart       bool
+	PeriodicInterval river.PeriodicSchedule
+
+	Arg CronJobArgInterface
 }