Error Detail when Creating User

[U8NWXD]

When creating a new account, users should be told what is wrong with their request. For example, if their username is already taken (results in 400 error with text Username already taken or invalid params), the user should be told so.

[U8NWXD]

To get the error text from the response, use

new String(error.networkResponse.data, StandardCharsets.UTF_8)