Auto fetch images from `upstream-source` about cos-lite-bundle HOT 3 CLOSED

Yes, that could be awesome @PietroPasotti.

render_bundle could have the urls to the metadata.yamls hardcoded and fetch from there.

However:

• We won't be able to render the bundle yaml without internet.
• When rendering a stable bundle, we won't know if the image in the charms' metadata is too new.

from cos-lite-bundle.

Also need to remember to update the bundle every time we update the images.
Submitted a doc update, but we probably need a periodic quality check for this @simskij.

from cos-lite-bundle.

We should update this manually when we notice it's off. There is not enough value in this to motivate building parse and replace automation for it.

from cos-lite-bundle.