Pluck Laravel collection by unique field (Typically User's First Name)

AppServiceProvider

public function boot(): void
{
    Collection::macro('pluckUnique', function (string $firstAttribute, string $secondAttribute, $glue = null) {

        return $this->map(function ($item) use ($firstAttribute, $secondAttribute) {
            $item->firstAttributeCleaned = Str::lower($item->{$firstAttribute});
            $item->secondattributeCleaned = Str::lower($item->{$secondAttribute});
            return $item;

        })->mapWithKeys(function ($value, $key) use ($firstAttribute, $secondAttribute, $glue) {
            if($glue) $key = $value->{$glue};

            if( $this->where('firstAttributeCleaned', $value->firstAttributeCleaned)->count() > 1 ){
                $secondAttributeLetter = Str::substr($value->secondattributeCleaned, 0, 1);
                if(
                    $this->where('firstAttributeCleaned', $value->firstAttributeCleaned)
                        ->filter(fn($item) => Str::startsWith($item->secondattributeCleaned, $secondAttributeLetter))
                        ->count() > 1
                ){
                    return [$key => $value->{$firstAttribute}.' '.$value->{$secondAttribute}];
                }
                return [$key => $value->{$firstAttribute}.' '.Str::upper($secondAttributeLetter).'.'];
            }
            return [$key => $value->{$firstAttribute}];
        });
    });
}

view.blade.php

{{ $users->pluckUnique('firstname', 'lastname')->implode(', ') }}

{{-- RENDER: unique first names OR first name + initial of last name if several identical first names OR full name if several identical first names & several identical initial of last names
Hugo, Tony, Sam E., Sam Albert, Sam Almost --}}