feat: api v9 and threads (#5570)

Co-authored-by: Noel <icrawltogo@gmail.com>
Co-authored-by: Amish Shah <dev@shah.gg>
Co-authored-by: Vlad Frangu <kingdgrizzle@gmail.com>
Co-authored-by: SynthGhost <60333233+synthghost@users.noreply.github.com>
Co-authored-by: SpaceEEC <24881032+SpaceEEC@users.noreply.github.com>
Co-authored-by: Elliot <elliot@maisl.fr>
Co-authored-by: Antonio Román <kyradiscord@gmail.com>
Co-authored-by: Sugden <28943913+NotSugden@users.noreply.github.com>

src/client/actions/ThreadMemberUpdate.js

@@ -0,0 +1,30 @@
+'use strict';
+
+const Action = require('./Action');
+const { Events } = require('../../util/Constants');
+
+class ThreadMemberUpdateAction extends Action {
+  handle(data) {
+    const client = this.client;
+    // Discord sends the thread id as id in this object
+    const thread = client.channels.cache.get(data.id);
+    if (thread) {
+      const member = thread.members.cache.get(data.user_id);
+      if (!member) {
+        const newMember = thread.members._add(data);
+        return { newMember };
+      }
+      const old = member._update(data);
+      /**
+       * Emitted whenever the client user's thread member is updated.
+       * @event Client#threadMemberUpdate
+       * @param {ThreadMember} oldMember The member before the update
+       * @param {ThreadMember} newMember The member after the update
+       */
+      client.emit(Events.THREAD_MEMBER_UPDATE, old, member);
+    }
+    return {};
+  }
+}
+
+module.exports = ThreadMemberUpdateAction;