I’m making adjustments to Working Copy, a Git client for iOS, phasing out usernames in API requests to use account_id instead.
This is working in most cases, but some users, especially newly created ones get an account_id in their authenticated /2.0/user response that seems invalid and gives 404 responses when used instead of usernames.
It specifically looks like valid account_id’s have the format INTEGER:UDID while invalid ones have the format [0-9a-f]{24}.
test@workingcopyapp.com is an example of a user account with what looks like an invalid account_id while anders@algoritmer.dk has a valid one that does not cause 404 errors when used instead of username.