User cannot replace embedded media link

[sabina-talipova]

Description

The user cannot replace the embedded media link, they must completely replace the entire embedded element. If a link is broken or the user wants to change it, they should be able to replace the link while leaving other settings as they are or change them if necessary.

Related issue

• https://github.com/silverstripe/silverstripe-asset-admin/issues/1344

Acceptance criteria

• [ ] User can open modal window with embedded media link, even if this link is broken
• [ ] User can modify any settings including media link
• [ ] User can save changes
• [ ] All AC's tested by e2e and Behat tests