add user management system

backend/app/schemas/user.py

@@ -0,0 +1,25 @@
+from pydantic import BaseModel, ConfigDict
+from typing import Optional
+from datetime import datetime
+
+class UserBase(BaseModel):
+    username: str
+    email: str
+    is_active: Optional[bool] = True
+    is_admin: Optional[bool] = False
+
+class UserCreate(UserBase):
+    password: str
+
+class UserUpdate(BaseModel):
+    username: Optional[str] = None
+    email: Optional[str] = None
+    is_active: Optional[bool] = None
+    is_admin: Optional[bool] = None
+    password: Optional[str] = None
+
+class UserResponse(UserBase):
+    id: int
+    created_at: datetime
+
+    model_config = ConfigDict(from_attributes=True)