Add Translation.value and .properties, with data model contents

[eemeli]

This builds on top of #3801, and will need a rebase.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 58.06452% with 65 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.85%. Comparing base (f6e2165) to head (87ef36f).

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