Fix: Change Customer schema datetime fields to str for proper serialization

app/models/schemas.py

@@ -2,7 +2,7 @@
 Pydantic Models and Schemas
 """
 
-from pydantic import BaseModel
+from pydantic import BaseModel, ConfigDict
 from typing import Optional
 from datetime import datetime
 
@@ -23,11 +23,10 @@ class CustomerCreate(CustomerBase):
 class Customer(CustomerBase):
     """Full customer schema"""
     id: int
-    created_at: datetime
-    updated_at: Optional[datetime] = None
+    created_at: str  # Changed from datetime to str for serialization
+    updated_at: Optional[str] = None  # Changed from datetime to str for serialization
     
-    class Config:
-        from_attributes = True
+    model_config = ConfigDict(from_attributes=True)
 
 
 class HardwareBase(BaseModel):