Swift Example doesn't support email login

[limouren]

Dev testing on an existing environment might not realise username and email might make a different. For those using email login, they just keep getting authentication error with no clues what has gone wrong.

[limouren]

A quick workaround would be to add a reminder to the project README / Swift Example README, with instruction to modify the code to work with email login (which requires a single-line change).