Extending "BelongsToMany" with custom default columns

To achieve the desired functionality, you can extend the BelongsToMany relationship in Laravel and customize it according to your needs. Here's how you can do it:

1. Create a new class that extends the BelongsToMany relationship class. Let's call it CustomBelongsToMany.

use Illuminate\Database\Eloquent\Relations\BelongsToMany;

class CustomBelongsToMany extends BelongsToMany
{
    /**
     * Attach a model to the parent with additional pivot data.
     *
     * @param  mixed  $id
     * @param  array  $attributes
     * @param  bool  $touch
     * @return void
     */
    public function attach($id, array $attributes = [], $touch = true)
    {
        $attributes = array_merge($attributes, [
            'created_by' => auth()->id(),
        ]);

        parent::attach($id, $attributes, $touch);
    }
}

1. Update your model's relationship method to return an instance of CustomBelongsToMany instead of BelongsToMany.

use App\CustomBelongsToMany;
use Illuminate\Database\Eloquent\Relations\BelongsToMany;

public function test(): BelongsToMany
{
    return (new CustomBelongsToMany(Test::class, 'pivot_table'))
        ->withPivot([
            'created_by',
            'notes',
        ])
        ->withTimestamps();
}

1. Now, you can use the sync method as usual, and the created_by column will automatically be populated with the authenticated user's ID.

$thing->sync([1, 2, 3]);

1. To handle the notes column, you can use the syncWithPivotValues method as you mentioned in your question.

$thing->syncWithPivotValues($arrayOfModels, ['notes' => $arrayOfNotes]);

By extending the BelongsToMany relationship and overriding the attach method, you can customize the behavior to automatically set the created_by column with the authenticated user's ID.