BUG: Cut/copy and paste allows duplicate URI

[pKallert]

Description

When using the cut and paste function it is possible to create a duplicate URL path segment.

Steps to Reproduce

1. Create a new page under home named 'Testing'
2. Create a new page under 'Testing' named 'Subpage' with the url path segment 'subpage'
3. Create a new shortcut under home named 'Subpage' with the url path segment 'subpage'
4. Publish everything
5. Structure should look like this now:
6. Use "Cut"-Feature of Neos UI to move the "Subpage" Shortcut from inside home to inside Testing:

Expected behavior

I would expect both the Subpage Page and the Subpage Shortcut to have different URL path segment or to get an error that I cannot move the Shortcut since the Path Segment is the same.

Actual behavior

You can move the node and have the same url two times. This can lead to very problematic situations like an endless loop if the shortcut is set to redirect to the "real" path.

Affected Versions

Neos: 8.3

UI: 8.3.4