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 = ""
  }

  private enum CodingKeys: CodingKey {
    case firstName
    case lastName
  }

  func encode(to encoder: any Encoder) throws {
    var container = encoder.container(keyedBy: User2.CodingKeys.self)

    try container.encode(self.firstName, forKey: User2.CodingKeys.firstName)
    try container.encodeIfPresent(self.lastName, forKey: User2.CodingKeys.lastName)
  }
}


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

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