The invoice print builder should switch the active language to the invoice language

Opened an MR with the patch from #13, let's see what the tests say.

I'm wondering if we aren't missing code similar to what we're doing in the PromotionOrderProcessor:

 if ($promotion->hasTranslation($content_langcode)) {
        $promotion = $promotion->getTranslation($content_langcode);
      }

And rely on the content langcode rather than the current language... But I'm going to trust that this has been tested... Fixed the tests, so will probably go ahead and commit this... Or just wait for the next release.

Or maybe just:
$current_langcode = $this->languageManager->getCurrentLanguage()->getId();
to
$current_langcode = $this->languageManager->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)->getId();

Automatically closed - issue fixed for 2 weeks with no activity.