add lazy option to outputs to delay execution of output if not needed

[jrichardlai]

What

Add lazy option to outputs to delay execution of output if not needed in all situation where the op is called.

Example:

class MyOp < ::Subroutine::Op

  outputs :heavy_operation, lazy: true

  protected

  def perform
    output :heavy_operation, -> { some_heavy_operation }
  end

  def some_heavy_operation
    # ...
  end

end

[cjhkim]

I believe this will mess with op_instance.outputs (which is a hash of all the outputs)

maybe outputs can be a method that calls any lazy outputs for backwards compatibility?

[jrichardlai]

Thanks updated