I am working on a Laravel 8 blogging application. The "Add article" form has a "switch" (checkbox) that lets the user choose whether or not the post will be a featured one.

The form:

<form method="POST" action="{{ route('dashboard.articles.add') }}" enctype="multipart/form-data" novalidate>
		@csrf

		<div class="col-md-12 @error('title') has-error @enderror">
			<input id="title" type="text" placeholder="Title" class="form-control @error('title') is-invalid @enderror" name="title" value="{{ old('title') }}" autocomplete="title" autofocus>

			@error('title')
					<span class="invalid-feedback" role="alert">
							<strong>{{ $message }}</strong>
					</span>
			@enderror
	</div>

	<div class="row mb-2">
		<label for="short_description" class="col-md-12">{{ __('Short description') }}</label>

		<div class="col-md-12 @error('short_description') has-error @enderror">
				<input id="short_description" type="text" placeholder="Short description" class="form-control @error('short_description') is-invalid @enderror" name="short_description" value="{{ old('short_description') }}" autocomplete="short_description" autofocus>

				@error('short_description')
						<span class="invalid-feedback" role="alert">
								<strong>{{ $message }}</strong>
						</span>
				@enderror
		</div>
	</div>

	<div class="row mb-2">
			<label for="category" class="col-md-12">{{ __('Category') }}</label>
		
			<div class="col-md-12 @error('category_id') has-error @enderror">
		
				<select name="category_id" id="category" class="form-control @error('category_id') is-invalid @enderror">
					<option value="0">Pick a category</option>
					@foreach($categories as $category)
						<option value="{{ $category->id }}">{{ $category->name }}</option>
					@endforeach
				</select>
		
					@error('category_id')
							<span class="invalid-feedback" role="alert">
									<strong>{{ $message }}</strong>
							</span>
					@enderror
			</div>
	</div>

	<div class="row mb-2">
		<div class="col-md-12 d-flex align-items-center switch-toggle">
				<p class="mb-0 me-3">Featured article?</p>
				<input id="featured" class="mt-1" type="checkbox" name="featured">
				<label class="px-1" for="featured">{{ __('Toggle') }}</label>
		</div>
	</div>

	<button type="submit" class="w-100 btn btn-primary">{{ __('Save') }}</button>

</form>

The controller:

class ArticleController extends Controller
{
	
	private $rules = [
		'category_id' => 'required|exists:article_categories,id',
		'title' => 'required|string|max:190',
		'short_description' => 'required|string|max:190',
	];

	private $messages = [
		'category_id.required' => 'Please pick a category for the article',
		'title.required' => 'Please provide a title for the article',
		'short_description.required' => 'The article needs a short description',
		'short_description.max' => 'The short description field is too long',
	];
	
	public function categories() {
		return ArticleCategory::all();
	}
	

	public function create() {
		// Load the view and populate the form with categories
		return view('dashboard/add-article',
			['categories' => $this->categories()]
		);
	}

    public function save(Request $request) {
		// Validate form (with custom messages)
		$validator = Validator::make($request->all(), $this->rules, $this->messages);

		if ($validator->fails()) {
			return redirect()->back()->withErrors($validator->errors())->withInput();
		}

		$fields = $validator->validated();

		// Turn the 'featured' field value into a tiny integer
		$fields['featured'] = $request->get('featured') == 'on' ? 1 : 0;


		// Data to be added
		$form_data = [
			'user_id' => Auth::user()->id,
			'category_id' => $fields['category_id'],
			'title' => $fields['title'],
			'slug' => Str::slug($fields['title'], '-'),
			'short_description' => $fields['short_description'],
			'featured' => $fields['featured'],
		];

		// Insert data in the 'articles' table
		$query = Article::create($form_data);

		if ($query) {
			return redirect()->route('dashboard.articles')->with('success', 'The article titled "' . $form_data['title'] . '" was added');
		} else {
			return redirect()->back()->with('error', 'Adding article failed');
		}
	}
}

The problem

When an attempt is made to submit the invalid form, the fields that are valid keep their values.

The unintended exception to the rule is the checkbox <input id="featured" class="mt-1" type="checkbox" name="featured">

What is my mistake?