Account created template language

This issue are related to user account notifications alone. The templates that are maintained in Security Console > User Categories

We have focus on templates regarding events of 'New user created'. The template have 2 locale: American/English and Danish.

Fusion/BPM is configured to notification mode: in-app and email (all)

When we create a contingent worker via My Client Groups > New Person > Add Contingent Worker, we would like to control the language to be used for this specific new user, when they receive email notification. We need to clarify, which logic is being used to determine the locale to be used for an outgoing mail notification to a specific user.