struct User1: Codable {
  let firstName: String
  let lastName: String?

  init(from decoder: any Decoder) throws {
    firstName = ""
    lastName = ""
  }
  func encode(to encoder: any Encoder) throws {}
}


struct User2: Codable {
  let firstName: String
  let lastName: String?

  init(from decoder: any Decoder) throws {
    firstName = ""
    lastName = ""
  }
}


struct User3: Codable {
  let firstName: String
  let lastName: String?

  func encode(to encoder: any Encoder) throws {}

  private enum CodingKeys: CodingKey {
    case firstName
    case lastName
  }

  init(from decoder: any Decoder) throws {
    let container: KeyedDecodingContainer<User3.CodingKeys> = try decoder.container(keyedBy: User3.CodingKeys.self)

    self.firstName = try container.decode(String.self, forKey: User3.CodingKeys.firstName)
    self.lastName = try container.decodeIfPresent(String.self, forKey: User3.CodingKeys.lastName)

  }
}