Allow unlocking user accounts by e-mail only

[jobara]

Describe the bug

While the username requirements are now configurable, a username is still required to unlock users. In the storytelling tool we are using the e-mail address for the username, so we don't actually need the username property at all. However, this function assumes the username based on how it parses the response from the call to that.byUsernameOrEmailReader.get.

Expected behavior

Because the searching for users handles lookup by username or email, unlocking should support both. Perhaps there is more general way to determine if the body returned contains the necessary data; which would allow more flexibility if the byUsernameOrEmailReader subcomponent is modified.