Add default orm cache settings if not set

Author: kayue

DependencyInjection/Configuration.php

@@ -28,7 +28,7 @@ public function getConfigTreeBuilder()
             ->scalarNode('cookie_domain')->defaultValue(null)->end()
             ->scalarNode('table_prefix')->defaultValue('wp_')->end()
             ->scalarNode('connection')->defaultValue('default')->end()
-            ->arrayNode('orm')->children()
+            ->arrayNode('orm')->addDefaultsIfNotSet()->children()
                 ->scalarNode('metadata_cache_pool')->defaultValue('cache.system')->end()
                 ->scalarNode('query_cache_pool')->defaultValue('cache.app')->end()
                 ->scalarNode('result_cache_pool')->defaultValue('cache.app')->end()