[5.4] update timestamp on soft delete only when its used

[themsaid]

This PR fixes the issue reported in #19620, the breaking change was introduced in #19538

This PR doesn't revert, but only updates the updated_at column if the Model's timestamps = true.

[kamui545]

Hello Mohamed,

Thank you for the fix.

I would like to point out that it will still break for people having the following kind of models:

class Example extends Model
{
    public $timestamps = true;
    const CREATED_AT = 'created_at';
    const UPDATED_AT = null; // Disable `updated_at` field
}

I'm pretty sure this use case is not recommended and then it will probably be a wont-fix, but I just wanted to make sure you are aware of it.

Thanks!

[bobbybouwmann]

@kamui545 If you don't want the updated_at field to be updated you don't need the field at all right? Instead you can only add a created_at field ;)

[kamui545]

@bobbybouwmann This is exactly the use case I am explaining, having no updated_at field in the table.