1. Create a PHP shell script that collects the placeholder names from the Twig templates and compares them to the message keys in each language. If message keys are missing or unused, the script must return a non-zero exit code and the templates must be listed ( grouped by language and grouped by unused/missing for each language).
2. Run the script as part of Travis validation of the content repository.

The templates use different translation files for different things, so it might be best to use the Twig Parser for analyzing the templates, to check if the right translation file is linked.

Background:

• Inspired by T157560