Allow nil for interfaces and models

[tfausak]

Fixes #263.

class InterfaceInteraction < ActiveInteraction::Base
  interface :anything

  def execute
    anything
  end
end

InterfaceInteraction.run!(anything: nil)
# master
#   ActiveInteraction::NoDefaultError: anything
# gh-263
#   => nil

class ModelInteraction < ActiveInteraction::Base
  model :object

  def execute
    object
  end
end

ModelInteraction.run!(object: nil)
# master
#   ActiveInteraction::NoDefaultError: object
# gh-263
#   => nil

[AaronLasseigne]

I'm not entirely clear on this. Why would we allow nil without a default being set?

[tfausak]

Because nil is an appropriate value. If you have an interface filter with no methods, nil implements that interface. If you have a model filter for Object, nil is an Object.

[tfausak]

Can I get a ?

[AaronLasseigne]