feat: implement LMS core (CMS, Courses, Enrollment, Progress, Auth) (Admin + API)

apps/common/api/base_serializer.py

@@ -0,0 +1,11 @@
+from rest_framework.serializers import ModelSerializer
+
+class BaseModelSerializer(ModelSerializer):
+    """
+    Base Serializer สำหรับ CMS‑like API
+    - ใช้ fields = "__all__" เป็น default
+    """
+
+    class Meta:
+        abstract = True
+        fields = "__all__"