Change local media attachments to perform heavy processing asynchronously (#13210)

Fix #9106

db/migrate/20200306035625_add_processing_to_media_attachments.rb

@@ -0,0 +1,5 @@
+class AddProcessingToMediaAttachments < ActiveRecord::Migration[5.2]
+  def change
+    add_column :media_attachments, :processing, :integer
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_01_26_203551) do
+ActiveRecord::Schema.define(version: 2020_03_06_035625) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -459,6 +459,7 @@ ActiveRecord::Schema.define(version: 2020_01_26_203551) do
     t.text "description"
     t.bigint "scheduled_status_id"
     t.string "blurhash"
+    t.integer "processing"
     t.index ["account_id"], name: "index_media_attachments_on_account_id"
     t.index ["scheduled_status_id"], name: "index_media_attachments_on_scheduled_status_id"
     t.index ["shortcode"], name: "index_media_attachments_on_shortcode", unique: true