fix(WebhookClient): use applyToClass instead of multiple inheritance (#1896)

src/structures/Webhook.js

@@ -8,21 +8,15 @@ const MessageEmbed = require('./MessageEmbed');
  * Represents a webhook.
  */
 class Webhook {
-  constructor(client, dataOrID, token) {
-    if (client) {
-      /**
-       * The client that instantiated the webhook
-       * @name Webhook#client
-       * @type {Client}
-       * @readonly
-       */
-      Object.defineProperty(this, 'client', { value: client });
-      if (dataOrID) this._patch(dataOrID);
-    } else {
-      this.id = dataOrID;
-      this.token = token;
-      Object.defineProperty(this, 'client', { value: this });
-    }
+  constructor(client, data) {
+    /**
+     * The client that instantiated the webhook
+     * @name Webhook#client
+     * @type {Client}
+     * @readonly
+     */
+    Object.defineProperty(this, 'client', { value: client });
+    if (data) this._patch(data);
   }
 
   _patch(data) {
@@ -274,6 +268,18 @@ class Webhook {
   delete(reason) {
     return this.client.api.webhooks(this.id, this.token).delete({ reason });
   }
+
+  static applyToClass(structure) {
+    for (const prop of [
+      'send',
+      'sendSlackMessage',
+      'edit',
+      'delete',
+    ]) {
+      Object.defineProperty(structure.prototype, prop,
+        Object.getOwnPropertyDescriptor(Webhook.prototype, prop));
+    }
+  }
 }
 
 module.exports = Webhook;