modify structure

server/src/app/models/metric.py

@@ -0,0 +1,12 @@
+from sqlmodel import Field, SQLModel, Relationship
+from src.app.models.question import Question
+
+#TODO : add pydantic validation
+
+class Metric(SQLModel, table=True):
+    id: int | None = Field(default=None, primary_key=True)
+    
+    question_id: int | None = Field(default=None, foreign_key="question.id", ondelete="CASCADE")
+    question: Question | None =  Relationship(back_populates="metrics")
+    
+    need_index: int