DeleteTitleDisplayName API call

I would like to be able to set a user's display name to null/empty. In other words, I would like to restore its display name to its default value.

My main use case for this is when we go from alpha testing to live, I want to preserve existing user accounts, but force them to choose new display names. I also want all alpha tester names to be freed so they can be used again.

I was planning to go about doing this by clearing their existing display names, since my lobby server currently already handles an empty/unset display name by giving the user a prompt to set their name.