Support for hanami-validations/dry-validations `rule(...)`

[Drowze]

In dry-validations and hanami-validations we can define arbitrary rules, which are particularly handy when defining a validation that acts on multiple attributes, e.g.:

class EventContract < Dry::Validation::Contract
  params do
    required(:start_date).value(:date)
    required(:end_date).value(:date)
  end

  rule(:end_date, :start_date) do
    key.failure('must be after start date') if values[:end_date] < values[:start_date]
  end
end

On hanami-controller, I see that we have support for a params block within actions, so we can wrap our request params within a hanami-validations params block and validate accordingly.
...But I don't see any way to use arbitrary rules on hanami-controller. Is it possible on Hanami 2?

I know it was possible in Hanami 1, e.g.:

module Api
  class MyAction
    include Api::Action
    params do
      required(:start).filled(:int?)
      required(:end).filled(:int?)

      rule(dates: %i[start_date end_date]) do |_start, _end|
        _end.gt?(value(:_start))
       end
     end

     def call(params)
       # ...
     end
  end
end

In Hanami 2 however, I'm currently simply using concrete classes inheriting from Dry::Validations::Contract and manually instantiating and validating the parameters, but I would like to see a more supported way if possible 🤔