How to Assign Roles Senior Manager Role using manager_id

In my Laravel-5.8, I have this API which I tried to consume and save using Guzzle

[
  {
   "date_of_birth": "2009-11-21T00:00:00",
    "first_name": "JAGUA",
    "last_name": "KING",
    "staff_id": "44444",
"senior_manager_id": "98876",
  },
  {
    "date_of_birth": "2005-11-21T00:00:00",
    "first_name": "JACKIE",
    "last_name": "LEE",
    "staff_id": "44444",
"senior_manager_id": "2222",
  },
]

Command

namespace App\Console\Commands; 
use Illuminate\Console\Command;

public function handle()
{       
    $client = new Client();
    $res = $client->request('GET','https://api.employees.net/allemployees', [
     'query' => ['key' => 'dfffgggggffffff']
   ])->getBody();

    $clientdatas = json_decode($res->getContents(), true);        

    foreach($clientdatas as $clientdata)
    {         
        Employee::updateOrCreate([
         'employee_code' => $clientdata->staff_id,
        ],
        [
            'first_name'                => $clientdata['first_name'],
            'last_name'                 => $clientdata['last_name'],
            'date_of_birth'             => Carbon::parse($clientdata['date_of_birth'])->toDateString(),
	'senior_manager_id'         => $clientdata['senior_manager_id'],
        ]);  

        $user = User::updateOrCreate([
            'email'                                 => $employee->email,

        ],
        [
            'first_name'                            => $employee->first_name,
            'last_name'                             => $employee->last_name,  
	'senior_manager_id'                     => $employee->senior_manager_id,     
        ]);      

        if (! $user->hasRole('Employee')) {
            $user->assignRole('Employee');  
        }        
    }           
}

From the code above, I have assigned Employee Role to each of the user using $user->assignRole('Employee').

However, I want to loop through all the the user table after I have saved all the data, check the field senior_manager_id in $user = User, and Assign the Role 'Senior Manager' $user->assignRole('Senior Manager') to the user where id = senior senior_manager_id.

        if (! $user->hasRole('Senior Manager')) {
            $user->assignRole('Senior Manager');  
        }     

This should only be done if it doesn't exits

How do I achieve this?

Thanks