bug #314 Add backward compatibility for old refund buses (Tomanhez)

This PR was merged into the 1.0-dev branch.

Discussion
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Based on configuration: https://github.com/Sylius/Sylius/blob/master/src/Sylius/Bundle/CoreBundle/Resources/config/app/messenger.yaml

Commits
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45eaeef Add backward compatibility for old buses

src/Resources/config/app/config.yml

@@ -32,12 +32,14 @@ sylius_mailer:
 framework:
     messenger:
         buses:
-            sylius.command_bus:
+            sylius.command_bus: &command_bus
                 middleware:
                     - 'validation'
                     - 'doctrine_transaction'
-            sylius.event_bus:
+            sylius.event_bus: &event_bus
                 default_middleware: allow_no_handlers
+            sylius_refund_plugin.command_bus: *command_bus
+            sylius_refund_plugin.event_bus: *event_bus
 
 winzou_state_machine:
     sylius_refund_refund_payment: