How where and when is unknown. There are many proposals and workarounds. Using this as a tracking ticker for other bugs and feature requests that should be solved by using the future file properties system.
See also [[mw:License integration]] which contains a proposal for storing file properties. The details of if and how this feature is coming should NOT be discussed on this bug!
Dependencies: Tickets that make this feature (im)possible
Blockers: Tickets that will use this system