Unsplash API requirements does not directly allow to store their images on
our server (We should use hotlinking unless the image is edited (cropped etc)).
Still, they have the `Image Beacon Alternative` to allow to store their images
on our server if we really need it with our use case.
With the Beacon Alternative, we should ping Unsplash server to notify an image
view.
To do so, we need to be able to recognize Unsplash imagesin the DOM, this is
why we are now using /unsplash/ in the URL.
The Unsplash image name should be the image ID as it will be the identifier
needed to ping their server.
This commit also adds credit to Unsplash in the media dialog next to the
unsplash input search.
It also add the `w-100` on the media dialog card as we lost that UI behavior
from BS3 to BS4.
opw-35060
closesodoo/odoo#27377
Romain Derie
40c6bc3ad2