Transfer Ownership of a summary / document

In some cases it will be necessary for summaries to change their owner while preserving comments / likes / id - especially for migration: E.g. when migrating from an old document collection to community solutions the owner of a document should be the original owner. In my opinion it would be preferable if an action from both sides is required. The original owner could create an OwnershipTransferRequest(summary: Summary, proposed_owner: str) which the proposed owner could accept, deleting all OwnershipTransferRequests on that summary and also also set the owner. Similarly OwnershipTransferRequests should be revokable and can obviously also be denied.