v5.9.3

• [#1834] Fix default allow_token_introspection returning false when a custom application_class is configured. The default proc compared application objects with ==, which fails when the authorized client and the introspected token's application are resolved as different classes (e.g. a base Doorkeeper::Application vs. a configured subclass) even though they reference the same record. It now compares application ids instead.
• [#1832] Fix confusing belongs_to :owner side effect: Doorkeeper::Models::Ownership is now included only when enable_application_owner? is set (read at include time), so models no longer expose a misleading owner association/reflection when the application owner feature is disabled and the schema lacks the owner columns.