[ACTIONS] on.schedule: create a new payload

do not reuse the payload of the event that triggered the creation of
the scheduled event. Create a new one instead that contains no other
information than the event name in the action field ("schedule").

(cherry picked from commit 0b40ca1ea5)

modules/structs/hook.go

@@ -402,6 +402,16 @@ func (p *PullRequestPayload) JSONPayload() ([]byte, error) {
 	return json.MarshalIndent(p, "", "  ")
 }
 
+type HookScheduleAction string
+
+const (
+	HookScheduleCreated HookScheduleAction = "schedule"
+)
+
+type SchedulePayload struct {
+	Action HookScheduleAction `json:"action"`
+}
+
 // ReviewPayload FIXME
 type ReviewPayload struct {
 	Type    string `json:"type"`

services/actions/notifier_helper.go

@@ -397,7 +397,11 @@ func handleSchedules(
 		return nil
 	}
 
-	p, err := json.Marshal(input.Payload)
+	payload := &api.SchedulePayload{
+		Action: api.HookScheduleCreated,
+	}
+
+	p, err := json.Marshal(payload)
 	if err != nil {
 		return fmt.Errorf("json.Marshal: %w", err)
 	}