default_value_for :preferred_language is not set with the config.i18n.default_locale value

Summary

Gitlab User model doesn't set preferred_language attribute from config.i18n.default_locale value.

GitLab: 12.0.3 (gitlab-ce@08a51a9db938bb05f9a4c999075d010079e16bad) GitLab Shell: 9.3.0 PostgreSQL: 10.7

Steps to reproduce

1. Set a default_locale in application.rb config.i18n.default_locale = :fr config.i18n.enforce_available_locales = false
2. Create a new user
3. User preferred_language attribute value is always English

What is the current correct behavior?

User default preferred_language attribute value should reflect the default locale

Current :

# with config.i18n.default_locale = :fr
default_value_for :preferred_language, I18n.default_locale
# preferred_language value is always :en

Expected:

default_value_for(:preferred_language) { I18n.default_locale } # bug fix
# preferred_language value is now :fr