[11.x] Cache token repository

[browner12]

Password reset tokens are a relatively short lived entity. Currently our only framework option is for them to be stored in the database. This is an okay option, but it's slightly annoying because it's another table to maintain, and makes it more difficult for Laravel to make desired adjustment if they require a schema change.

This PR proposes a new CacheTokenRepository which will allow the password reset tokens to be handled via cache. IMO cache is a perfect storage medium because it can be more ephemeral, just like the password reset tokens.

To enable this new CacheTokenRepository, adjust your config/auth.php like so:

'passwords' => [

    //new cache driver
    'customers' => [
        'driver'   => 'cache',
        'store'    => 'passwords',
        'provider' => 'customers',
        'expire'   => 60,
        'throttle' => 60,
    ],

   //default old database driver
    'users'     => [
        'provider' => 'users',
        'table'    =>'password_reset_tokens',
        'expire'   => 60,
        'throttle' => 60,
    ],
],

The driver key will activate the new "cache" driver. The store key is optional, although I would recommend creating a dedicated cache store for your password resets to prevent flushing your password resets when refreshing your normal cache. The expire and throttle key behave as before.

If your application has multiple "providers" that all use email as their identifier, you also get the added benefit of being able to place them on separate cache stores, thus avoiding an unlikely but possible collision.