Support Drupal 9

With #2 we are using $this->t() and $this->messenger in a static function, i.e. we are not in object context.

I also think we do not need the newly introduced dependency injections at all:

• MessengerInterface $messenger is only used in public static function changeAuthorActionFinishedCallback(), so not in object context.
• TranslationInterface $stringTranslation is not used at all (because #2 also has "use StringTranslationTrait" which would be enough for the call to $this->t() in the same function ...
• ... but this also happens in the static function, so we cannot reference $this at all

There is still one untranslated string 'Changing author...' in public static function updateFields().

This considered I think we should revert this commit (and $message = 'Changing author...'; to $message = t('Changing author...');.

Or did I get something wrong?

Patch coming.

I opened 🐛 $this called in non object context - revert #3197015 and add missing translation Active .