Laravel unique for all undeleted

<?php
/*
* Use Case: 
* You have multiple deleted_at items that share an attribute that is supposed to be unique, 
* for example, a username in a user's table, and are using model-level validation and watson/validation
*
* In this use case, you want to ignore ALL deleted items when considering uniqueness.
* 
* The current `unique` validation rule doesn't seem to do this, even when you add the extra 
* columns and ignored fields, e.g.:
* 
* 'username' => 'required|string|min:2|unique:users,username,NULL,deleted_at',
*
* Let's say our username is 'snipe'. 
*
* If you have ONE deleted user with the username 'snipe', this will pass validation.
* 
* If you have MORE THAN ONE deleted user with the username 'snipe', this will fail validation
* disallowing any new user's with that username to be saved. This is obviously a problem, since
* that user will never be able to be saved since it inherently breaks Laravel's built-in
* `unique` validation. 
*
* Using this custom validator, we would use this as the validation rule:
*
* 'username' => 'required|string|min:2|unique_undeleted',
* 
* where the field following `unique_undeleted:` is the table name we should be querying 
* the attribute name against.
*
* This code would go in the AppServiceProvider, in the `boot()` method.
* 
* You'll need to add an entry into the `validation.php` language file, like:
*  "unique_undeleted" => "The :attribute must be unique.",
* 
*/


// In AppServiceProvider.php
Validator::extend('unique_undeleted', function($attribute, $value, $parameters, $validator) {

    $count = DB::table($parameters[0])->select('id')->where($attribute,'=',$value)->whereNull('deleted_at')->where('id','!=',$parameters[1])->count();

    if ($count < 1) {
        return true;
    } else {
        return false;
    }

});

// In app/Http/Traits/UniqueUndeletedTrait.php

<?php
namespace App\Http\Traits;

trait UniqueUndeletedTrait
{

    /**
    * Prepare a unique_ids rule, adding a model identifier if required.
    *
    * @param  array  $parameters
    * @param  string $field
    * @return string
    */
    protected function prepareUniqueUndeletedRule($parameters, $field)
    {
        // Only perform a replacement if the model has been persisted.
        if ($this->exists) {
            return 'unique_undeleted:'.$this->table.','. $this->getKey();
        }

        return 'unique_undeleted:'.$this->table.',0';
    }
}