アプリ内課金でCodableを利用する ref: https://qiita.com/MTattin/items/3d5507efc39e73cd57f1

file0.swift

///
/// ReceiptDetail
///
struct ReceiptDetail: Codable {
    let receipt_type: String
    let adam_id: Int
    let app_item_id: Int
    let bundle_id: String
    let application_version: String
    let download_id: Int
    let version_external_identifier: Int
    let receipt_creation_date: String
    let receipt_creation_date_ms: String
    let receipt_creation_date_pst: String
    let request_date: String
    let request_date_ms: String
    let request_date_pst: String
    let original_purchase_date: String
    let original_purchase_date_ms: String
    let original_purchase_date_pst: String
    let original_application_version: String
    let in_app: [ReceiptInfo]
}
///
/// ReceiptInfo
///
struct ReceiptInfo: Codable {
    let quantity: String
    let product_id: String
    let transaction_id: String
    let original_transaction_id: String
    let purchase_date: String
    let purchase_date_ms: String
    let purchase_date_pst: String
    let original_purchase_date: String
    let original_purchase_date_ms: String
    let original_purchase_date_pst: String
    let expires_date: String
    let expires_date_ms: String
    let expires_date_pst: String
    let web_order_line_item_id: String
    let is_trial_period: String
}

file1.swift

///
/// ReceiptInfo - Auto-renewable subscriptions
///
struct ReceiptInfo: Codable {
    let quantity: String
    let product_id: String
    let transaction_id: String
    let original_transaction_id: String
    let purchase_date: String
    let purchase_date_ms: String
    let purchase_date_pst: String
    let original_purchase_date: String
    let original_purchase_date_ms: String
    let original_purchase_date_pst: String
    let expires_date: String
    let expires_date_ms: String
    let expires_date_pst: String
    let web_order_line_item_id: String
    let is_trial_period: String
}

file2.swift

///
/// ReceiptInfo - Non-Consumable
///
struct ReceiptInfo: Codable {
    let quantity: String
    let product_id: String
    let transaction_id: String
    let original_transaction_id: String
    let purchase_date: String
    let purchase_date_ms: String
    let purchase_date_pst: String
    let original_purchase_date: String
    let original_purchase_date_ms: String
    let original_purchase_date_pst: String
    let is_trial_period: String
}

file3.swift

    let expires_date: String
    let expires_date_ms: String
    let expires_date_pst: String
    let web_order_line_item_id: String

file4.swift

///
/// ReceiptInfo
///
struct ReceiptInfo: Codable {
    let quantity: String
    let product_id: String
    let transaction_id: String
    let original_transaction_id: String
    let purchase_date: String
    let purchase_date_ms: String
    let purchase_date_pst: String
    let original_purchase_date: String
    let original_purchase_date_ms: String
    let original_purchase_date_pst: String
    var expires_date: String?                   /// Non-Consumable には存在しない
    var expires_date_ms: String?                /// Non-Consumable には存在しない
    var expires_date_pst: String?               /// Non-Consumable には存在しない
    var web_order_line_item_id: String?         /// Non-Consumable には存在しない
    let is_trial_period: String
}

file5.swift

    latest_receipt_info
    latest_receipt

file6.swift

struct Receipt: Codable {
    let status: Int
    let environment: String
    let receipt: ReceiptDetail
    var latest_receipt_info: [ReceiptInfo]?
    var latest_receipt: String?