Fixed missing validation error for password

[akulmehta]

When a user tries to login and enters the wrong password, the authentication fails and the sendFailedLoginResponse is triggered. Previously this function only throws a ValidationException with the email field, causing the error message of auth.failed which in default Laravel app is "These credentials do not match our records." to only appear below the email input field, and does not show any invalidity in the UI in the password field, even if the password field is what was incorrect (I observed this when using Bootstrap scaffolding). As a result this would make the user feel that the incorrect input was the email address rather than the password.

This PR is an attempt to fix this issue by adding the password field to the ValidationException. By doing this, the error bag contains the password field and appropriate invalid message and UI elements are shown.

Tests are edited accordingly.

[akulmehta]

Note - I chose to use the same error i.e. auth.failed as this is already part of core Laravel. But maybe the core Laravel message for auth.failed should read "One or more of these credentials do not match our records.". I am not sure how errors are handled by other authentication packages (Fortify) so not sure if I should touch that. But this is easy to customize by editing the language file too.

[taylorotwell]

It's fine as is.

[akulmehta]

@taylorotwell Please reconsider. If the user enters the wrong password, the email field shows the error. The user ends up thinking that their email address is wrong.

[akulmehta]

This is what the UI looks like when the password is wrong: