Allow UDs to be claimed by linked identity
Identity owner_key is the one used to perform identity operations like certifications. It would be convenient if linked identity could claim UD on their own account instead of the one managing the identity. This would allow to have less secure everyday account that can claim the UD and keep account managing the identity in a safer place without needing to periodically claim the ud and transfer it to other account.
I'm simply writing it for discussion, but maybe a proxy account would be a better general option.