Upgrade Doorkeeper to 4.4.1 (#8197)

db/migrate/20171201000000_change_account_id_nonnullable_in_lists.rb

@@ -1,5 +1,3 @@
-require Rails.root.join('lib', 'mastodon', 'migration_helpers')
-
 class ChangeAccountIdNonnullableInLists < ActiveRecord::Migration[5.1]
   def change
     change_column_null :lists, :account_id, false

db/migrate/20180814171349_add_confidential_to_doorkeeper_application.rb

@@ -0,0 +1,23 @@
+require Rails.root.join('lib', 'mastodon', 'migration_helpers')
+
+class AddConfidentialToDoorkeeperApplication < ActiveRecord::Migration[5.2]
+  include Mastodon::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  def up
+    safety_assured do
+      add_column_with_default(
+        :oauth_applications,
+        :confidential,
+        :boolean,
+        allow_null: false,
+        default: true # maintaining backwards compatibility: require secrets
+      )
+    end
+  end
+
+  def down
+    remove_column :oauth_applications, :confidential
+  end
+end