Translations only cover the public UI.

1. Create a new translation file using POEdit
2. Click on "Update from POT" option
3. Select messages.pot as the source file
4. Add your translations
5. Save file as locale-name.po (POEdit should autogenerate locale-name.mo as well)
6. Make a pull request or send the po-file to [email protected]

Field validation error message translations can be found and edited from the joi-messages project.