Allow for configuration of which login route to use

[Robert M]

I am happy to do the leg work as required, but wanted to get a feeling for whether a PR would be acceptable before I began.

We have multiple authentication in our Laravel app, and for passport we require the users authenticate via a secondary login route (for clarity our primary login is /login and the desired passport login is /sso/login.

I believe if we were to extend those places where an Laravel\Passport\Exceptions\AuthenticationException is thrown to utilize the existing redirectTo property on the base Illuminate\Auth\AuthenticationException to direct the user to be logged in via the correct route.

e.g.

class CheckClientCredentialsForAnyScope extends CheckCredentials
{
    /**
     * Validate token credentials.
     *
     * @param  \Laravel\Passport\Token  $token
     * @return void
     *
     * @throws \Laravel\Passport\Exceptions\AuthenticationException
     */
    protected function validateCredentials($token)
    {
        if (! $token) {
            throw new AuthenticationException(redirectTo: config('passport.login_route'));
        }
    }

I envisage the route name being an optional config value that can be configured in passport.php

[Dries Vints]

Heya. Honestly, just feel free to attempt a PR to see if Taylor would accept it 👍