Mobile MDLab

Precondiiton: User on the registration screen

When User adds a Username and leaves the input field focus then the Username should be validated¶

• username has to be at least six characters in length and not longer then 15 characters.
• username can only contain alphanumeric characters (letters A-Z, numbers 0-9) with the exception of underscores. (We won't allow User to type other characters).

Error messages:
* Your username is too short. It has to be 6-15 characters.
* Your username is too long. It has to be 6-15 characters.

API validation
If the Username is correct, then is has to be verified in DB. When User leaves the input field and Username is correct the APi request hast to be done to check whether the new username is already exist or not.
Error message in case Username is already exist in DB: "Sorry.. The username is already taken."

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mockups: 2.Registration