anchor.diff:    |> serialize
     |> OK
   
  +let urlWithHost (request : HttpRequest) =
  +  let host = request.headers |> List.find (fst >> (=) "host") |> snd
  +  sprintf "%s://%s%s" request.url.Scheme host request.url.PathAndQuery
  +
   let getTodo id =
     match find id with
     | Some todo -> serialize todo |> OK
  
positive.code:     |> propertyInfo.GetValue
      |> unbox
    
    match find request.url.AbsoluteUri with
    | Some todo ->
      store.Remove todo |> ignore
      let getPatchedProperty expr = getPatchedProperty expr patchedTodo todo
  
negative.code:     |> UTF8.to_string'
      |> deserialize<Todo>
    
    let todo = { todo with url = (request |> urlWithHost, Guid.NewGuid()) ||> sprintf "%s%O" }
    store.Add todo
    todo
    |> serialize
  