Improve Login Form design

[AlexOreshkevich]

We need to have responsible design for Login form that would have beautiful look on different devices including desktop and mobile phones, ie. would be responsible.

Use RWA feature of Vaadin 14 and Polymer 3 to make that happen.

Pick up one of the appropriate templates from the web and provide non-escapable dialog box that would appear each time user need to log in.

From functional requirements perspective we should have the following:

• Login / Sign Up separate screens
• username / password basic textboxes
• OAuth sources login (Facebook, Google etc)
• Remember me
• Forgot password

Sign up should redirect on separate RegistrationView form.

Consider the following as a very good example:

General UI/UX requirements:

• Adopt Google Material Design standards and best practices
• https://vaadin.com/blog/responsive-design

[kate-novik]

Improvements of existing Login form:

1. Migrate Polymer element to Lit Element because the future version of Vaadin recommends to use Lit Element (for increasing performance).
   See Lit+Vaadin
2. Add support of Responsive Design.
3. Support A11Y (some helpful information from WAI-ARIA).
4. Create a reusable component for social buttons.
5. Add "Remember Me" checkbox.
6. Add "Fogot password" link/button.

All information about using Vaadin 14 you can find in Vaadin14-tutorial