handle config already loaded before patching

If another plugin already accesses OpenProject::Configuration before the
patch is applied, the cost_reporting_cache_filter_classes method is
never generated as the effect of the patch is then only to set a default
value.

lib/open_project/reporting/patches/open_project/configuration_patch.rb

@@ -24,7 +24,23 @@ module OpenProject::Reporting::Patches
   module OpenProject::ConfigurationPatch
     def self.included(base)
       base.class_eval do
+        extend ModuleMethods
+
         @defaults['cost_reporting_cache_filter_classes'] = true
+
+        if config_loaded_before_patch?
+          @config['cost_reporting_cache_filter_classes'] = true
+        end
+      end
+    end
+
+    module ModuleMethods
+      def config_loaded_before_patch?
+        @config.present? && !@config.has_key?('cost_reporting_cache_filter_classes')
+      end
+
+      def cost_reporting_cache_filter_classes
+        @config['cost_reporting_cache_filter_classes']
       end
     end
   end