Allow customizing field to use with login procedure

[al3nzy6]

Question	Answer
Pull request type	ENHANCEMENT
License	MIT

What's in this PR?

I don't want to use Email as field to login, I want to customize it, so I have add to adminlte config username_field in this package in view login.blade.php also change the field of username. Before it was only email now it has been able to customize.

Developer must add new function in LoginController:

protected function username() {
    return config('adminlte.username_field');
}

Checklist

• I tested these changes.

[dfsmania]

These changes introduces some bugs, first only a set of possible values are accepted by the input type attribute, so it can not be anything, note $username variable may hold any string name. Second, the translation entry __('adminlte::adminlte.username') does not currently exists.

[dfsmania]

Hi @al3nzy6 , the idea is nice however we need to take into consideration other things:

1. When this package was created, there was only one authentication scaffolding around Laravel, and it was Laravel/UI, so the package was intended to provide an easy way to integrate with it.

2. Now there are more advanced authentication scaffoldings around, like Breeze and Jetstream which this package does not support by default. So, to not overcomplicate maintenance of the package, we just opted to allow publishing all the package resources and let the final user customize anything for their integration with any of these new auth scaffolding.

Now, I assume you have only tested these changes with legacy laravel/ui authentication scaffolding right? If that's the case I will try to look into this when I get some time, maybe we can approach to a better solution...