Sign webhook requests (#4156)

Co-authored-by: Tom Moor <tom.moor@gmail.com>

server/queues/tasks/DeliverWebhookTask.ts

@@ -209,12 +209,20 @@ export default class DeliverWebhookTask extends BaseTask<Props> {
       paranoid: false,
     });
 
+    let data = null;
+    if (model) {
+      data = {
+        ...presentWebhookSubscription(model),
+        secret: undefined,
+      };
+    }
+
     await this.sendWebhook({
       event,
       subscription,
       payload: {
         id: event.modelId,
-        model: model && presentWebhookSubscription(model),
+        model: data,
       },
     });
   }
@@ -540,6 +548,12 @@ export default class DeliverWebhookTask extends BaseTask<Props> {
           env.VERSION ? `/${env.VERSION.slice(0, 7)}` : ""
         }`,
       };
+
+      const signature = subscription.signature(JSON.stringify(requestBody));
+      if (signature) {
+        requestHeaders["Outline-Signature"] = signature;
+      }
+
       response = await fetch(subscription.url, {
         method: "POST",
         headers: requestHeaders,