Sometimes circulation managers change their URLs. This can happen because of a move from HTTP to HTTPS, because a hosting provider changed, or because something changed about the library's domain name policy.

Here's a procedure that allows a circulation manager to re-register itself using its old address:

1. library registers with registry using a shared secret that doesn't match the existing URL (edited)
2. registry runs all the basic checks – does the new URL have an auth document, etc
3. registry creates a Hyperlink on the library with rel="start", containing the new auth document URL
4. registry sends out a validation email to the integration contact email. "hey, someone tried to change the url of your circ manager, click here if it was you"
5. upon validation, the library.url is updated to the hyperlink.href and the hyperlink is deleted
6. then the auth document is re-imported as it would be in a normal registration step

This is mostly work on the registry side; the circulation manager just needs to be able to handle the status message that says something like "it looks like you're trying to change the URL of the circ manager, check your email"