UHF-10120: Add language to request + UHF-9289 fixes backend error messages in frontend

[sundflux]

UHF-10120

What was done

• This adds language parameter for hakuvahti to react side. It was removed from backend. Part of same branch in rekry drupal side:

City-of-Helsinki/drupal-helfi-rekry#498

How to install

• Make sure your instance is up and running on latest dev branch.
  • git pull origin dev
  • make fresh
• Update the HDBT theme
  • composer require drupal/hdbt:UHF-10120
• Run make drush-cr

How to test

• Check that frontend doesn't show error messages from backendend, rather showing generic error. For example try submitting invalid for backend, but valid for frontend email, like foo@bar

Continuous documentation

• This feature has been documented/the documentation has been updated
• This change doesn't require updates to the documentation

Translations

• Translations have been added to .po -files and included in this PR

Other PRs

City-of-Helsinki/drupal-helfi-rekry#498

[github-actions]

⚠️ Visual regression found! Please check if this change is wanted or accidental. You can check the output here: https://city-of-helsinki.github.io/drupal-hdbt/pull/1006/html_report/

[teroelonen]

This works nicely 🦖