Save multiple checkbox inputs with additional data to pivot table

I'm trying to assign licence categories with expiry date input for each category to a user. I'm working with Laravel 8 and Bootstrap 5.

Up to assigning categories to a user I'm ok. The lack of knowledge starts with saving that expiry date to additional column in pivot table.

So here's my form section where I collect necessary information:

<div class="mb-1"><strong>Assign user's driving licence categories:</strong></div>
@foreach($categories as $category)
	<div class="input-group mb-3">
		<div class="input-group-text" style="width: 6ch !important;">{{$category->name}}</div>
		<div class="input-group-text">
		<input class="form-check-input" type="checkbox" name="categories[]" value="{{$category->id}}">
		</div>
		<div class="input-group-text">Expiry date</div>
		<input class="form-control" type="date" name="expiry_date[]">
	</div>
@endforeach

And Controller:

public function store(Request $request)
{
        $request->validate([
            'first_name' => 'required',
            'last_name' => 'required',
            'email' => 'required',
            'roles' => 'required',
            'categories' => 'required',
            'expiry_date' => 'required_with:categories'
        ]);
                
        $user = User::create($request->except(['roles', 'categories', 'expiry_date']))
            ->drivingLicenceCategory()->sync($request->categories);

	return redirect()->route('users.index')->with('success', 'User added successfully.');
}

I have no idea how to assign expiry date to each category. Also what if category of id = 1 is not selected? The second array of expiry_date is returning null in position [0] :(

Hope someone can help and thank you for your time spent helping me :)