* Keep the user on login page on failure
* Show an error if username already exists
* Check the password format in the backend
* Return a better message if username is invalid
* Add a title to the login page
* wip: Improve look of login and register pages
* Set a capital M in username help message
On the registration page, username tip started with a minuscule, while
the password tip started with a capital.
* Change message if username is taken
* Extract hashPassword method from userController
* Extract and refactor fever key-related methods
* Move update of API password to dedicated action
* Simplify the controller by refactoring feverUtil
* Add locales
