FIX: adds chat-draw-expanded class to body (#28490)

To achieve this, the code is now using bodyClass instead of relying on the addChatDrawerStateCallback`.

plugins/chat/assets/javascripts/discourse/components/chat-drawer.hbs

@@ -1,3 +1,11 @@
+{{#if this.chatStateManager.isDrawerActive}}
+  {{bodyClass "chat-drawer-active"}}
+{{/if}}
+
+{{#if this.chatStateManager.isDrawerExpanded}}
+  {{bodyClass "chat-drawer-expanded"}}
+{{/if}}
+
 {{#if this.chatStateManager.isDrawerActive}}
   <div
     data-chat-channel-id={{this.chat.activeChannel.id}}

plugins/chat/assets/javascripts/discourse/initializers/chat-setup.js

@@ -157,14 +157,6 @@ export default {
         id: "chat",
       });
 
-      api.addChatDrawerStateCallback(({ isDrawerActive }) => {
-        if (isDrawerActive) {
-          document.body.classList.add("chat-drawer-active");
-        } else {
-          document.body.classList.remove("chat-drawer-active");
-        }
-      });
-
       api.addAboutPageActivity("chat_messages", (periods) => {
         const count = periods["7_days"];
         if (count) {

plugins/chat/spec/system/drawer_spec.rb

@@ -112,11 +112,14 @@ RSpec.describe "Drawer", type: :system do
     it "collapses the drawer" do
       visit("/")
       chat_page.open_from_header
+
       expect(page).to have_selector(".chat-drawer.is-expanded")
+      expect(page).to have_selector("body.chat-drawer-expanded")
 
       page.find(".c-navbar").click
 
       expect(page).to have_selector(".chat-drawer:not(.is-expanded)")
+      expect(page).to have_selector("body:not(.chat-drawer-expanded)")
     end
   end