Canvis a "Add instant input validation on authentication forms"

Is your feature request related to a problem? Please describe.
Users need to send the form in order to see if they made a mistake. Here are some pain points that were raised in user interview.

• Reloading the page each time which makes the user
• start form the top which feels like doing it all over again as the user has to scroll to see the error messages
• retype the password twice
• Error messages are not always easy to understand
• Users who made multiple errors feel overwhelmed by all the red field and error message

Describe the solution you'd like
Use instant input validation on the form so we can dynamically show the user errors as she is typing (without having to send the form and scroll the whole thing) so she can correct herself one error at a time.

The fields that are subject to this feature are :

• Nickname 
  As a user who is typing her nickname I get an error if I add a space or a special special character
  
  
• Password
  As a user who is typing her password I can see password conditions turn green as I go. (Here is a good example (External link) (External link), if you start typing a password you'll see a tooltip. This is related to this Meta proposal (External link) (External link))
• Email
  As a user who type an email I get an error if I input a space or a special character that cannot be used in an email adress [any other condition ?)

Describe alternatives you've considered
No

Additional context
This proposal is part of a larger scope to improve authentication flow in Decidim. Working document here.

Does this issue could impact on users private data?
No

Funded by
OSP and Angers