[Feature Request] Validate User Credentials & show validation status message

[sbmsr]

What you need to do

Our login form needs to show a message for 2 cases:

1. The user has logged in successfully.
2. The user failed to provide valid credentials.

Please add this feature to our form submission handler. Valid credentials can be found here.

Expected behavior

1. Our form should handle authentication success, like so:

2. Our form should handle authentication failure, like so: