Users can claim their own invites

[ComputerElite]

Description

When creating a share invite without specifying a user just the invite id gets shown. Using redeem code with the id you get does not yield a cannot claim own share error. Instead the api accepts it and you've now got a share with yourself.

Steps to reproduce (https://next.openshock.app)

1. Open User Shares
2. Create new share with any limits and no user
3. In the invites tab copy the invite id
4. Use the redeem code button to redeem the invite