Fix various issues around OpenGraph representation of media (#14133)

- Fix audio attachments not being represented in OpenGraph tags
- Fix audio being represented as "1 image" in OpenGraph descriptions
- Fix video metadata being overwritten by paperclip-av-transcoder
- Fix embedded player not using Mastodon's UI
- Fix audio/video progress bars not moving smoothly
- Fix audio/video buffered bars not displaying correctly

app/models/media_attachment.rb

@@ -194,15 +194,17 @@ class MediaAttachment < ApplicationRecord
 
     x, y = (point.is_a?(Enumerable) ? point : point.split(',')).map(&:to_f)
 
-    meta = file.instance_read(:meta) || {}
+    meta = (file.instance_read(:meta) || {}).with_indifferent_access.slice(:focus, :original, :small)
     meta['focus'] = { 'x' => x, 'y' => y }
 
     file.instance_write(:meta, meta)
   end
 
   def focus
-    x = file.meta['focus']['x']
-    y = file.meta['focus']['y']
+    x = file.meta&.dig('focus', 'x')
+    y = file.meta&.dig('focus', 'y')
+
+    return if x.nil? || y.nil?
 
     "#{x},#{y}"
   end
@@ -219,12 +221,11 @@ class MediaAttachment < ApplicationRecord
   before_create :prepare_description, unless: :local?
   before_create :set_shortcode
   before_create :set_processing
+  before_create :set_meta
 
   before_post_process :set_type_and_extension
   before_post_process :check_video_dimensions
 
-  before_save :set_meta
-
   class << self
     def supported_mime_types
       IMAGE_MIME_TYPES + VIDEO_MIME_TYPES + AUDIO_MIME_TYPES
@@ -306,15 +307,11 @@ class MediaAttachment < ApplicationRecord
   end
 
   def set_meta
-    meta = populate_meta
-
-    return if meta == {}
-
-    file.instance_write :meta, meta
+    file.instance_write :meta, populate_meta
   end
 
   def populate_meta
-    meta = file.instance_read(:meta) || {}
+    meta = (file.instance_read(:meta) || {}).with_indifferent_access.slice(:focus, :original, :small)
 
     file.queued_for_write.each do |style, file|
       meta[style] = style == :small || image? ? image_geometry(file) : video_metadata(file)