[Bug]: The relationship between a Notification and Order should be one-to-one

[loevgaard]

Plugin version

master

Sylius version

1.10

What happened?

@leflings pointed out that the relationship between a Notification and Order should be one-to-one:

https://github.com/Setono/SyliusAbandonedCartPlugin/blob/master/src/Resources/config/doctrine/model/Notification.orm.xml#L25-L27

If this is changed, we should also check if there already exists a relationship when creating the notification, so we don't accidentally creates a database exception

Relevant log output

No response