[Feature Request] Custom metadata argument in change plan request

Currently, the GO SDK or the APIs do not support passing any custom metadata when calling the change plan workflow. This becomes a problem in the following scenario.

Step 1: I create a subscription

Step 2: I update the subscription by calling Change Plan to include an add-on

Step 3: I update the subscription again by calling Change Plan to include an add-on

Step 4: I received one failure and one success webhook event

Step 5: There is no way for me to tell which webhook event corresponds to which action in my system/application

Ideally, in all the async systems, there must be a request id or some kind of identifier that can then be used when consuming the event asynchronously to tie back the output with the initial set of actions.

Having the capability to pass metadata or generate the ID for actions that would then trigger corresponding webhook does help the systems to integrate more seamlessly