Multilanguage support

Problem/Motivation

If you have a translated entity refeference field of, for instance, a "tag" vocabulary, you can choose different terms in each translation, but in taxomony_index also in this module, all terms are shared between languages.

Steps to reproduce

Proposed resolution

Add new field in the database table for langcode, build the taxonomy index for each transaltion. Maybe we can use like a reserved word "all / default" or something like that if we don't want add each varation if the target field is not translatable.

Remaining tasks

User interface changes

API changes

Data model changes