Convert a temporary upload into a permanent upload that does not expire.
key is required to identify the permanent upload.
Use this endpoint when you want to reuse a file across multiple envelopes without re-uploading it each time. For example, store a company logo or a contract template that you reference repeatedly.
retention changes from temporary to permanent and the expires_at property is removed. The upload id and url remain the same.200 OK status code and an upload object with retention set to permanent, or an error otherwise.