Attributing deleted user's comments and issues to another.
### Description
I'm about to delete an account on Gitlab.com as I realised I had two accounts. I've opened up some important issues that need addressing, but when I delete this account, those comments / issues will disappear into the ether.
### Proposal
I'm sure - I've seen this on other platforms, but when you delete an account, you can choose which other user to attribute all issues and comments too. From a permissions stand point, you could attribute them to the owner of the group - with a small subtext detailing `originally by X`. However, I would like them to be attributed to my other account. So one could pick a user, they would then have to confirm the transfer (probably similar to the forgot password mechanism) send the new user a token in an email address to confirm.
### Links / references
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Deleting an account has the following effects:
All user content like authored issues, snippets, comments will be removed
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