Add CRUD operations for users with tests and fixtures

Implemented user CRUD operations including creation, retrieval, updating, and deletion through a generic CRUD base class. Enhanced user schemas with additional attributes and created tests to verify functionality, covering edge cases such as duplicates and pagination. Updated the test suite with new fixtures and methods to support the tests.

backend/app/crud/user.py

@@ -0,0 +1,56 @@
+# app/crud/user.py
+from typing import Optional, Union, Dict, Any
+from sqlalchemy.orm import Session
+from app.crud.base import CRUDBase
+from app.models.user import User
+from app.schemas.users import UserCreate, UserUpdate
+from app.core.auth import get_password_hash
+
+
+class CRUDUser(CRUDBase[User, UserCreate, UserUpdate]):
+    def get_by_email(self, db: Session, *, email: str) -> Optional[User]:
+        return db.query(User).filter(User.email == email).first()
+
+    def create(self, db: Session, *, obj_in: UserCreate) -> User:
+        db_obj = User(
+            email=obj_in.email,
+            password_hash=get_password_hash(obj_in.password),
+            first_name=obj_in.first_name,
+            last_name=obj_in.last_name,
+            phone_number=obj_in.phone_number if hasattr(obj_in, 'phone_number') else None,
+            is_superuser=obj_in.is_superuser if hasattr(obj_in, 'is_superuser') else False,
+            preferences={}
+        )
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def update(
+            self,
+            db: Session,
+            *,
+            db_obj: User,
+            obj_in: Union[UserUpdate, Dict[str, Any]]
+    ) -> User:
+        if isinstance(obj_in, dict):
+            update_data = obj_in
+        else:
+            update_data = obj_in.model_dump(exclude_unset=True)
+
+        # Handle password separately if it exists in update data
+        if "password" in update_data:
+            update_data["password_hash"] = get_password_hash(update_data["password"])
+            del update_data["password"]
+
+        return super().update(db, db_obj=db_obj, obj_in=update_data)
+
+    def is_active(self, user: User) -> bool:
+        return user.is_active
+
+    def is_superuser(self, user: User) -> bool:
+        return user.is_superuser
+
+
+# Create a singleton instance for use across the application
+user = CRUDUser(User)