constructor(scheme: String, realm: String) : this(scheme, singletonMap("realm", realm))

  init {
    val newAuthParams = mutableMapOf<String?, String>()
    for ((key, value) in authParams) {
      val newKey = key?.lowercase(US)
      newAuthParams[newKey] = value
    }
    this.authParams = unmodifiableMap<String?, String>(newAuthParams)
  }

  /** Returns a copy of this charset that expects a credential encoded with [charset]. */