Unable to create or modify a Draft API redirect

Symptoms

When using GET to fetch a redirect, you receive “error_message”: “no redirect found"
When using PUT to modify a redirect, you receive "{url} is a circulation URL and can’t be used as an external redirect"
When using POST to create a redirect, you receive "{url} already exists for website {site}"

Cause

The URL belongs to a story in circulation. Redirects cannot be created for URLs of circulated stories.

Solution

De-circulate the story by removing all circulations for it in Composer. Unpublishing without de-circulating will not free the URL.
Reattempt to create the redirect.

More Information

Draft API - Production