Allow sharing a private metadata with a permalink

## Issue
It's not easy to share metadatas which are not fully public. To share it to someone, the target user has to be registered in the platform, be in the correct group etc..

## Proposal
I would like that a metadata editor can share a metadata with a generated link, no matters if the target user is registered or not in the platform.
It would be like in google drive for instance, with the option "**everyone with the link can view the document**".

## Additional context
We would like to make the development of this feature, but prefer to check before if this feature sounds reasonable for you ?
What do you think about its doability and what technical advice would you give as a starting point ?

Thanks for your inputs @fxprunayre & @josegar74

The issue does not identify any files, tests, or entry points. Start by clarifying the access rules and lifecycle for a permalink that exposes private metadata, then locate the metadata permission and sharing flows. Done should include an agreed design and an implemented, tested link-based viewing path.

Written by the indexing model from the issue text.