moved models to separate folder

app/models/constraint.py

@@ -0,0 +1,10 @@
+from pydantic import BaseModel
+from typing import Optional
+
+class Constraint(BaseModel):
+  key: str
+  value: str
+  field_id: Optional[int]
+  option_id: Optional[int]
+  minimum: int
+  maximum: int