perf: reduce Configuration instances to the bare minimum

Author: ElMassimo

lib/inertia_rails/configuration.rb

@@ -53,6 +53,12 @@ def merge(config)
       Configuration.new(**@options.merge(config.options))
     end
 
+    # Internal: Finalizes the configuration for a specific controller.
+    def with_defaults(config)
+      @options = config.options.merge(@options)
+      freeze
+    end
+
     OPTION_NAMES.each do |option|
       define_method(option) {
         evaluate_option @options[option]

lib/inertia_rails/controller.rb

@@ -40,7 +40,7 @@ def use_inertia_instance_props
       def _inertia_configuration
         @_inertia_configuration ||= begin
           config = superclass.try(:_inertia_configuration) || ::InertiaRails.configuration
-          @inertia_config ? config.merge(@inertia_config.freeze).freeze : config
+          @inertia_config&.with_defaults(config) || config
         end
       end