Meta: Update to django 3.2

• fix dark theme clash with custom bootstrap in admin interface
• fix 'Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'. HINT: Configure the DEFAULT_AUTO_FIELD setting or the AkmodelConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.' issues on check
• check for further compatibility issues