Mutually exclusive options in OptionGroup

[daring2]

Hello,

Is it possible to use mutually exclusive options (mutuallyExclusiveOptions) inside OptionGroup class?

Example:

class TestOptions: OptionGroup() {
    val test by mutuallyExclusiveOptions(
        option("--p1"),
        option("--p2"),
    )
}

In this example I get the following compiler error:

Property delegate must have a 'getValue(TestOptions, KProperty<*>)' method. None of the following functions is suitable: 
public open fun getValue(thisRef: CliktCommand, property: KProperty<*>): String? defined in com.github.ajalt.clikt.parameters.groups.MutuallyExclusiveOptions

[ajalt]

This has been asked before in #393. Nested groups are not supported.