CurrencyCode.kt

inline class CurrencyCode private constructor(private val isoCode: String) {

  override fun toString(): String = isoCode

  companion object {
    fun from(isoCode: String): CurrencyCode {
      require(isoCode.matches("^[A-Za-z]{3}$".toRegex())) {
        "Invalid ISO 4217 currency code format: $isoCode"
      }
      return CurrencyCode(isoCode.toUpperCase(Locale.ROOT).intern())
    }
  }
}