Reworded the docs about storing sessions in database

Author: javiereguiluz

_build/redirection_map

@@ -479,3 +479,5 @@
 /components/translation/custom_formats https://github.com/symfony/translation
 /components/translation/custom_message_formatter https://github.com/symfony/translation
 /components/routing https://github.com/symfony/routing
+/doctrine/pdo_session_storage /session/database
+/doctrine/mongodb_session_storage /session/database

doctrine.rst

@@ -853,10 +853,9 @@ Learn more
     doctrine/custom_dql_functions
     doctrine/dbal
     doctrine/multiple_entity_managers
-    doctrine/pdo_session_storage
-    doctrine/mongodb_session_storage
     doctrine/resolve_target_entity
     doctrine/reverse_engineering
+    session/database
     testing/database
 
 .. _`Doctrine`: https://www.doctrine-project.org/