feat: add default manager to AppModelMixin

Author: liuruibin

apps/common/mixins/app_model_mixin.py

@@ -10,6 +10,8 @@
 
 
 class AppModelMixin(models.Model):
+    objects = models.Manager()
+
     create_time = models.DateTimeField(verbose_name="创建时间", auto_now_add=True, db_index=True)
     update_time = models.DateTimeField(verbose_name="修改时间", auto_now=True, db_index=True)