Have some trouble getting all available locales in Symfony 3. 
The idea is to create a custom language switcher.

I have

```
parameters:
locale: en
app.locales: en|fr|ru

```

I can get requested locale or user stored in session locale.
But how can i get all parameters.app.locales in Service of Controller on finally in Twig? So that i can have ar array like en|fr|ru and so on.

Thanks.