Messages are done. Works good

Please, no under_scored variables, use CamelCase instead, http://symfony.com/doc/current/contributing/code/standards.html#naming-conventions
Create a custom FormType for it so that you can create a simple MessageType for a new message
You should declare this form type as a service and inject ```@security.context```.
In ```toUser``` field you should define a custom QueryBuilder which will fetch all the users except current one - this will prevent writing to yourself issue.