Odoo by default propagate language field to the created contacts from their
form, but it doesn't allow to change it once created.

This module fills this gap, and also provides other facilities for the
contact language management:

#. Put the language of the parent company when the contact doesn't have a
   language and this parent company is assigned.
#. When the company changes the language, it fills with the same language all
   the contacts that don't have any.
#. Show the language in the inner narrowed Contact form and
   set the new conctact with a different language if needed.
#. Search and also group contacts by their language.