Featured Video form does not enable Save button after entering a YouTube URL

[amandasramalho]

Description
When adding a Featured Video to a book record, the form does not allow the user to save the entry after a YouTube URL has been entered.

[tosteiner]

currently only available for Obelisk, Sphinx and Pyramid customers - as only self-hosted video files can be pointed to here.

Consider: introduce option to add external links to videos