Preview canceled subscriptions via API

[terashi]

Preview payments for an exsiting subscritpoin works well on Web UI, but not via API. An empty amendment preview is a workaround to show it, but it doesn't work for a subscription scheduled to be cancleded.

We'd like to have a preview call for a subscritpion lik Web UI.

[jb832]

We have a few situations where we need to show the user the adjustment that will be made if they cancel the current subscription and purchase a new subscription. If we could preview all of that together via the API (or successfully get them separately) and have the amounts and the tax correct, that would be great. 

[nharlow]

We are updating the subscription preview API and currently plan to include this as a supported use case. Thanks for ths input.