[Feature] Ablity to write custom change detection logic for custom doctrine types

[Arkemlar]

Feature Request

What

Currently, during changeset computation, instances of custom types are compared by === comparison.
My proposal makes it possible to override this behavior. To do so, there must be a way to define a function that does only one thing: compares two values before-and-after.

Why

I seen lots of questions from doctrine users in git hub and stackoverflow like "why changes not detected when I use custom doctrine type?".
And the only answer was: override entity's property with new instance. Well, that's good and correct when we use value objects. But in other cases this is kind of rude way to do things, I think. And sometimes it is painful to write lots of extra code. So my approach reduces pain.

How

I see multiple ways to implement it:

1. When I write custom type class with convertToPHPValue and convertToDatabaseValue methods, I could also write compareValues it will be called instead of using === for comparison. Example:

class SomeCustomType extends Type
{
    public function convertToPHPValue($value, AbstractPlatform $platform) {}
    public function convertToPHPValue($value, AbstractPlatform $platform) {}
    public function compareValue($valueA, $valueB) {
        return $valueA == $valueB;
    }
}

2. Another way is to add extra field to ORM\Column annotation where I can define comparator - reference to a static function, like so:

    #[ORM\Column(comparator: [SomeClass::class, 'compare'])]
    private SomeCustomType $field;

My personal like to first one by many means.

[Arkemlar]

If it's fine, I might implement it.

[arno14]

See #5542 (comment)