Get l10n within NewUserMailHelper to ensure it always uses the new user's language.
Some related tests had to be changed because they relied on internals, see also from the PHPUnit documentation:
"Exercise caution when using [the at] matcher as it can lead to brittle tests which are too closely tied to specific implementation details."
Signed-off-by: Zulan <git@zulan.net>
$emailTemplate->addBodyText($this->l10n->t('Welcome to your %s account, you can add, protect, and share your data.',[$this->themingDefaults->getName()]));
$emailTemplate->addBodyText($this->l10n->t('Your username is: %s',[$userId]));
$emailTemplate->addBodyText($l10n->t('Welcome to your %s account, you can add, protect, and share your data.',[$this->themingDefaults->getName()]));
$emailTemplate->addBodyText($l10n->t('Your username is: %s',[$userId]));
if($generatePasswordResetToken){
$leftButtonText=$this->l10n->t('Set your password');
$leftButtonText=$l10n->t('Set your password');
}else{
$leftButtonText=$this->l10n->t('Go to %s',[$this->themingDefaults->getName()]);
$leftButtonText=$l10n->t('Go to %s',[$this->themingDefaults->getName()]);