Multiple URLs for the same item #462
Description
Is your feature request related to a problem? Please describe.
At the moment, a CSL entry can only have 1 explicit URL (and more implicit ones via doi, pmid, ...). This is unreliable: Primary copies can go down, secondary copies like archives can be temporarily unavailable or go down; even when the resource is in the public interest.
Describe the solution you'd like
Allow to specify multiple URLs at once via making the URL variable an array. The canonical one could be first with the rest following.
Describe alternatives you've considered
Keep the URL variable as a scalar string/dict and introduce a new variable archive-URLs (name to be bikeshed) instead. That would be backward-compatible.
Additional context
This stems from a discussion on https://codeberg.org/DI-Day/quellensammlung/pulls/2#issuecomment-11825871: Some companies are known to engage against reporting and achieve temporary takedowns until legal proceedings even though the content is just fine, old servers may go down due to a lack of financial/personal resources; we want to prevent a scenario where research is blocked because of this.