DEV: Create a site setting for video thumbnails (#21266)

Creating a way to disable the auto generation of video thumbnails.

app/assets/javascripts/discourse/app/mixins/composer-video-thumbnail-uppy.js

@@ -18,6 +18,9 @@ export default Mixin.create(ExtendableUploader, UppyS3Multipart, {
 
   @bind
   _generateVideoThumbnail(videoFile, uploadUrl) {
+    if (!this.siteSettings.video_thumbnails_enabled) {
+      return;
+    }
     let video = document.createElement("video");
     video.src = URL.createObjectURL(videoFile.data);
 

config/site_settings.yml

@@ -1568,6 +1568,10 @@ files:
     default: false
     client: true
     hidden: true
+  video_thumbnails_enabled:
+    default: true
+    client: true
+    hidden: true
 
 trust:
   default_trust_level: