如何使用新的UIButton配置方式在按钮上添加阴影？

问：

我正在尝试重构应用程序中的按钮。以前，按钮上的阴影可以使用类似的属性轻松实现。但是，使用新的配置样式，我不确定如何在按钮上创建阴影。layer.shadowColor

我试图在谷歌上搜索解决方案，但不幸的是，我找不到任何解决方案。

public class MainButton: UIButton {

override init(frame: CGRect) {
    super.init(frame: frame)
    setup()
}

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    setup()
}

private func setup() {
    var config = UIButton.Configuration.borderedTinted()
    config.baseBackgroundColor = .red
    config.buttonSize = .medium
    config.cornerStyle = .capsule

    let handler: UIButton.ConfigurationUpdateHandler = { [self] button in
        switch button.state {
        case .highlighted:
            button.configuration?.baseBackgroundColor = .blue
        default:
            button.configuration?.baseBackgroundColor = .red
        }
    }

    config.titleTextAttributesTransformer =
    UIConfigurationTextAttributesTransformer { [self] incoming in
        var outgoing = incoming
        outgoing.font = UIFont().withSize(16)
        outgoing.foregroundColor = isEnabled ? .white : .gray
        return outgoing
    }

    config.contentInsets = .init(top: 4, leading: 4, bottom: 4, trailing: 4)
    configuration = config
    configurationUpdateHandler = handler
}

override var isEnabled: Bool {
    didSet {
        var updatedConfiguration = self.configuration
        updatedConfiguration?.background.backgroundColor = .clear
        self.configuration = updatedConfiguration
    }
}

}