Improve username handling on login related screens

[hithacker]

Sewa rural users were changing tablets recently and were facing lots of issues in logout and login due to the way we handle username input.

Issues:

1. If user enters space anywhere in the username we show an error saying 'Username is incorrect, please correct it'. If users enters space in the end of username by mistake, they find this error message impossible to understand because they can not see the space and error message also do not convey any useful information.
2. In case where user logs out and tries to login again if they enter the same username that was logged in previously but one or multiple letters in the username they are entering is in different case then they get a message saying Multiple users cannot login
   
   This makes it confusing from them as they are just trying to login into the same device they were logged in earlier.
3. Sometimes they enter the first letter of username in capital unknowingly since some keyboards capitalizes the first letter of the word. So they get the error saying Authentication failure.

Possible solutions

1. Don't let the user input space in the username or password field. Suggested by Sid.
2. We save usernames in lowercase only in db and in Cognito. Or we give a better error message that users can understand and also in local language.
3. Same as 2.