Add a create_user method for register data

src/api/users.py

@@ -30,6 +30,12 @@ class RegisterData(BaseModel):
     password: Annotated[str, StringConstraints(min_length=1, max_length=50)]
     email: EmailStr
 
+    async def create_user(self) -> User:
+        """Create a new user in the database."""
+        password_hash = create_password_hash(self.password)
+        user = User(username=self.username, email=self.email, password_hash=password_hash)
+        return await user.create()
+
 
 @final
 class UserData(BaseModel):
@@ -93,9 +99,7 @@ async def register(reg_data: Annotated[RegisterData, Body()]) -> UserData:
     if user is not None:
         raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail="Username already taken")
 
-    password_hash = create_password_hash(reg_data.password)
-    user = User(username=reg_data.username, email=reg_data.email, password_hash=password_hash)
-    user = await user.insert()
+    user = await reg_data.create_user()
     return UserData.from_user(user)