Failed to sort on Lens view with Tag field

[kichetof]

• Laravel Version: 12.9.2
• Nova Version: 5.5.3
• PHP Version: 8.4.6
• Reproduction Repository: https://github.com/kichetof/nova-issue-6806

Description:

When you add a Tag field to a Lens, you can't sort columns.

[2025-04-18 09:58:49] local.ERROR: Call to undefined method Illuminate\Database\Eloquent\Relations\BelongsToMany::getForeignKey() {"userId":1,"exception":"[object] (BadMethodCallException(code: 0): Call to undefined method Illuminate\\Database\\Eloquent\\Relations\\BelongsToMany::getForeignKey() at /Users/tof/Herd/nova-issue-6806/vendor/laravel/framework/src/Illuminate/Support/Traits/ForwardsCalls.php:67)

According to this #6311 (comment), lens should be used to display flattened data, and BelongsToMany isn't flattened. But, I think that Tag field is the "flattened view" of a belongsToMany. What do you think?

Detailed steps to reproduce the issue on a fresh Nova installation:

Uncomment this code and sort UserLens view with any columns.

https://github.com/kichetof/nova-issue-6806/blob/2ea23cd0d1f05b02b3a7d9c3d7efab53eb085982/app/Nova/User.php#L69-L75