feat: Add global MODELTRANSLATION_REQUIRED_LANGUAGES setting

Refs #743

docs/modeltranslation/registration.rst

@@ -101,9 +101,9 @@ say it in code::
 Of course multiple inheritance and inheritance chains (A > B > C) also work as
 expected.
 
-However, if the base class is not abstract, inheriting the ``TranslationOptions`` will 
-cause errors, because the base ``TranslationOptions`` already took care of adding 
-fields to the model. The example below illustrates how to add translation fields to a 
+However, if the base class is not abstract, inheriting the ``TranslationOptions`` will
+cause errors, because the base ``TranslationOptions`` already took care of adding
+fields to the model. The example below illustrates how to add translation fields to a
 child model with a non-abstract base::
 
     from modeltranslation.translator import translator, TranslationOptions
@@ -119,7 +119,7 @@ child model with a non-abstract base::
     translator.register(NewsWithImage, NewsWithImageTranslationOptions)
 
 
-This will add the translated fields ``title`` and ``text`` to the ``News`` model and further add 
+This will add the translated fields ``title`` and ``text`` to the ``News`` model and further add
 the translated field ``image`` to the ``NewsWithImage`` model.
 
 .. note:: When upgrading from a previous modeltranslation version (<0.5), please
@@ -289,6 +289,11 @@ For German, all fields (both ``title`` and ``text``) are required; for all other
 
     The required fields are still ``null=True``, though.
 
+.. versionadded:: 0.20
+
+To set required_languages for all models, use `MODELTRANSLATION_REQUIRED_LANGUAGES` setting,
+which accepts the same values as `required_languages` class variable.
+
 
 ``TranslationOptions`` attributes reference
 -------------------------------------------

modeltranslation/settings.py

@@ -3,7 +3,7 @@
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 
-from ._typing import AutoPopulate
+from ._typing import AutoPopulate, _ListOrTuple
 
 TRANSLATION_FILES: tuple[str, ...] = tuple(
     getattr(settings, "MODELTRANSLATION_TRANSLATION_FILES", ())
@@ -21,6 +21,8 @@
     raise ImproperlyConfigured("MODELTRANSLATION_DEFAULT_LANGUAGE not in LANGUAGES setting.")
 DEFAULT_LANGUAGE = _default_language or AVAILABLE_LANGUAGES[0]
 
+REQUIRED_LANGUAGES: _ListOrTuple[str] = getattr(settings, "MODELTRANSLATION_REQUIRED_LANGUAGES", ())
+
 # Fixed base language for prepopulated fields (slugs)
 # (If not set, the current request language will be used)
 PREPOPULATE_LANGUAGE: str | None = getattr(settings, "MODELTRANSLATION_PREPOPULATE_LANGUAGE", None)

modeltranslation/translator.py

@@ -102,7 +102,9 @@ class TranslationOptions(metaclass=FieldsAggregationMetaClass):
     ``related_fields`` contains names of reverse lookup fields.
     """
 
-    required_languages: ClassVar[_ListOrTuple[str] | dict[str, _ListOrTuple[str]]] = ()
+    required_languages: ClassVar[_ListOrTuple[str] | dict[str, _ListOrTuple[str]]] = (
+        mt_settings.REQUIRED_LANGUAGES
+    )
 
     def __init__(self, model: Model) -> None:
         """