Add separate cache directory for non-local uploads (#12821)

db/migrate/20200417125749_add_storage_schema_version.rb

@@ -0,0 +1,9 @@
+class AddStorageSchemaVersion < ActiveRecord::Migration[5.2]
+  def change
+    add_column :preview_cards, :image_storage_schema_version, :integer
+    add_column :accounts, :avatar_storage_schema_version, :integer
+    add_column :accounts, :header_storage_schema_version, :integer
+    add_column :media_attachments, :file_storage_schema_version, :integer
+    add_column :custom_emojis, :image_storage_schema_version, :integer
+  end
+end