Laravel: user id is not added as Foreignkey - php

Question

I want that a user can create e.g. a football club. When the logged in user creates the club (with an Input-field) the foreignkey should automatically appear in the table of the club.
User
User Modell
class User extends Authenticatable
{
use Notifiable;
protected $fillable = [
'name',
'email',
'password',
];
public function wgGroup()
{
return $this->hasOne('WgGroup','user_id');
}
}
WgGroup e.g. for example to create a club
WgGroup Controller
class WGController extends Controller
{
public function dashboard()
{
return view('verified.dashboard');
}
public function createWG(Request $request)
{
$wg = new WgGroup();
$wg->wg_name = $request->wg_name;
$wg->user_id = User::find($request['id']);
$wg->save();
if($wg != null){
return redirect()->back()->with(session()->flash('alert-success', 'Your wg are createt'));
}
return redirect()->back()->with(session()->flash('alert-danger', 'Something went wrong!'));
}
}
WgGrup Model
class WgGroup extends Model
{
use HasFactory;
protected $table = 'wg_groups';
protected $fillable = [
'wg_name', 'user_id'
];
public function user() {
return $this->belongsTo('User');
}
}
WgGroup Database
class CreateWgGroups extends Migration
{
/**
* Run the migrations.
*
* #return void
*/
public function up()
{
Schema::create('wg_groups', function (Blueprint $table) {
$table->id();
$table->string('wg_name');
$table->foreignId('user_id')->nullable()->constrained('users')->onDelete('set null');
$table->timestamps();
});
}
/**
* Reverse the migrations.
*
* #return void
*/
public function down()
{
Schema::dropIfExists('wg_groups');
}
}
I don't know exactly why the FK user_id is not added directly to the database.
public function user() {
return $this->belongsTo('User');
}
I thought through this function would happen.