Potential broken links in Migrate to Volto's Default Pages

[shogunbr]

When migrating to Volto, the migration process offers a very neat feature to migrate Folders to Folderish Pages. Additionally, it allows merging the Default Pages of Folders with the replacing Folderish Pages. However, there is an issue with broken links that may occur when the Default Page is deleted.

Consider the following structure:

├── A Folder
│   ├── Default Page
└── Another Page

If there is a link in "Another Page" referencing the UUID of the "Default Page", the link will break after the migration process because the "Default Page" gets deleted.
To address this, it would be beneficial to include a link-checking and updating mechanism during the migration process. This mechanism should update all links referencing the "Default Page" old UUID with the UUID of the parent Folderish Page before deleting the "Default Page".