Allow Tag withPreview to be set conditionally

[kichetof]

Hello,

It would be really great to add a callback to withPreview to let us decide when we want to allow it.
When your index contain a lot of tags, they are too many queries that slow everything when preview is enable.

Adding something like peekable of BelongsTo:

->withPreview(function (NovaRequest $request) {
    return $request->isResourceDetailRequest();
}),

And by default, it's true:

public function withPreview($callback = true)
{
    $this->withPreview = $callback;

    return $this;
}

public function isPreviewable(NovaRequest $request)
{
    if (is_callable($this->withPreview)) {
        $this->withPreview = call_user_func($this->withPreview, $request);
    }

    return $this->withPreview;
}

public function jsonSerialize(): array
{
    /** @phpstan-ignore-next-line */
    return with(app(NovaRequest::class), function ($request) {
        return array_merge([
           /*
           ....
           */
            'withPreview' => $this->isPreviewable($request), // update withPreview too
        ], parent::jsonSerialize());
    });
}

Hope you'll add something like that :)
Thanks for all!

[kichetof]

It'll also be useful to determine if user can see the data to avoid 403 redirect