Exchange dropped Action.HTTP in favor of Action.Execute, which doesn't have a URL property.
Setting up an Actionable Messages App allow multiple/regex targets.
In real-life scenario, same message may have different target for each button and may include, for example message id:
https://my-server/api/decline_message/3?because=so. https://my-server/api/confirm_message/3.
This cannot be done this way any more, and an Adaptive Card now is restricted to one URL from the app that created it.