Writes a model's further-language texts: the owning module
calls it from its own write action, in that action's transaction — it opens none and commits none. Shaped as the
Operation the audited execution introduces: one entry point, the model and the payload, no side effect outside the
database. It refuses a field the model's #[Translatable] does not name, the base language (that is the column's)
and a language that is not one of the tenant's further languages. An empty text removes the translation.