[MM-63325, MM-63329] feat: dont register plugins or show the footer i…

…f MMEMBED cookie is set to `1` (mattermost#30393)

* feat: no-op register plugin if MMEMBED=1
* feat: disable footer links when MMEMBED=1

webapp/channels/src/components/header_footer_route/footer.tsx

@@ -15,6 +15,11 @@ const Footer = () => {
 
     const {AboutLink, PrivacyPolicyLink, TermsOfServiceLink, HelpLink} = useSelector(getConfig);
 
+    // Check if MMEMBED cookie is set and if so, don't show the footer
+    if (document.cookie.includes('MMEMBED=1')) {
+        return null;
+    }
+
     return (
         <div className='hfroute-footer'>
             <span

webapp/channels/src/plugins/index.ts

@@ -62,6 +62,11 @@ window.plugins = {};
 // During the beta, plugins manipulated the global window.plugins data structure directly. This
 // remains possible, but is officially deprecated and may be removed in a future release.
 function registerPlugin(id: string, plugin: Plugin): void {
+    // Don't register plugins if MMEMBED cookie is set
+    if (document.cookie.includes('MMEMBED=1')) {
+        return;
+    }
+
     const oldPlugin = window.plugins[id];
     if (oldPlugin && oldPlugin.uninitialize) {
         oldPlugin.uninitialize();