Remove deprecated use of session-based language handling

Session-based language handling is deprecated in Django 3.x and will be
removed in 4.x.

https://docs.djangoproject.com/en/3.2/topics/i18n/translation/#explicitly-setting-the-active-language

babybuddy/middleware.py

@@ -9,16 +9,17 @@ from django.utils import timezone
 class UserTimezoneMiddleware:
     """
     Sets the timezone based on a user specific setting that falls back on
-    `settings.TIME_ZONE`.
+    `settings.TIME_ZONE`. This middleware must run after
+    `django.contrib.auth.middleware.AuthenticationMiddleware` because it uses
+    the request.user object.
     """
     def __init__(self, get_response):
         self.get_response = get_response
 
     def __call__(self, request):
-        timezone_name = request.session.get('user_timezone')
+        if hasattr(request.user, 'settings') and request.user.settings.timezone:
-        if timezone_name:
             try:
-                timezone.activate(pytz.timezone(timezone_name))
+                timezone.activate(pytz.timezone(request.user.settings.timezone))
             except pytz.UnknownTimeZoneError:
                 pass
         return self.get_response(request)

babybuddy/models.py

@@ -3,11 +3,10 @@ import pytz
 
 from django.conf import settings
 from django.contrib.auth.models import User
-from django.contrib.auth.signals import user_logged_in
 from django.db import models
 from django.db.models.signals import post_save
 from django.dispatch import receiver
-from django.utils import timezone, translation
+from django.utils import timezone
 from django.utils.text import format_lazy
 from django.utils.translation import gettext_lazy as _
 
@@ -101,15 +100,3 @@ def create_user_settings(sender, instance, created, **kwargs):
 @receiver(post_save, sender=User)
 def save_user_settings(sender, instance, **kwargs):
     instance.settings.save()
-
-
-@receiver(user_logged_in)
-def user_logged_in_callback(sender, request, user, **kwargs):
-    if user.settings.language:
-        translation.activate(user.settings.language)
-        # TODO: Change this behavior as session-based language is deprecated.
-        request.session[
-            translation.LANGUAGE_SESSION_KEY] = user.settings.language
-    if user.settings.timezone:
-        timezone.activate(user.settings.timezone)
-        request.session['user_timezone'] = user.settings.timezone

babybuddy/settings/base.py

@@ -61,11 +61,11 @@ MIDDLEWARE = [
     'whitenoise.middleware.WhiteNoiseMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
     'babybuddy.middleware.RollingSessionMiddleware',
-    'django.middleware.locale.LocaleMiddleware',
+    'django.contrib.auth.middleware.AuthenticationMiddleware',
     'babybuddy.middleware.UserTimezoneMiddleware',
+    'django.middleware.locale.LocaleMiddleware',
     'django.middleware.common.CommonMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',
-    'django.contrib.auth.middleware.AuthenticationMiddleware',
     'django.contrib.messages.middleware.MessageMiddleware',
     'django.middleware.clickjacking.XFrameOptionsMiddleware',
     'axes.middleware.AxesMiddleware',
@@ -161,14 +161,14 @@ TIME_ZONE = os.environ.get('TIME_ZONE') or 'UTC'
 
 USE_I18N = True
 
-LANGUAGE_CODE = 'en'
+LANGUAGE_CODE = 'en-US'
 
 LOCALE_PATHS = [
     os.path.join(BASE_DIR, "locale"),
 ]
 
 LANGUAGES = [
-    ('en', _('English (US)')),
+    ('en-US', _('English (US)')),
     ('en-GB', _('English (UK)')),
     ('nl', _('Dutch')),
     ('fr', _('French')),

babybuddy/views.py

@@ -18,7 +18,6 @@ from django_filters.views import FilterView
 from babybuddy import forms
 from babybuddy.mixins import LoginRequiredMixin, PermissionRequiredMixin, \
     StaffOnlyMixin
-from babybuddy.models import user_logged_in_callback
 
 
 class RootRouter(LoginRequiredMixin, RedirectView):
@@ -145,7 +144,6 @@ class UserSettings(LoginRequiredMixin, View):
             user_settings = form_settings.save(commit=False)
             user.settings = user_settings
             user.save()
-            user_logged_in_callback(UserSettings, request, user)
             messages.success(request, _('Settings saved!'))
             return set_language(request)
         return render(request, self.template_name, {