[BUG] Document.sync() ignores Link fields

[ADR-007]

Describe the bug
Document.sync() method doesn't sync Link fields.

To Reproduce

class A(Document):
    v: int = 1

class B(Document):
  a: Link[A]
  aa: list[Link[A]]

b = B(A(), [A()])
await b.save()

await B.update({}, {B.a: A(v=2), B.aa: [A(v=3), A(v=4)])

await b.sync()

assert b.a.v == 2 # fail
assert b.aa[0].v == 3 # fail

Expected behavior
Sync should refresh linked values as well.
It can be done by changing merge_models function,
Or by passing fetch_links, with_children, nesting_depth, nesting_depths_per_field fields to sync function that should be propagated to document = await self.find_one({"_id": self.id})

Additional context
This is because it uses merge_models function:
beanie/odm/utils/parsing.py

def merge_models(left: BaseModel, right: BaseModel) -> None:
    """
    Merge two models
    :param left: left model
    :param right: right model
    :return: None
    """
    from beanie.odm.fields import Link

    for k, right_value in right.__iter__():
        left_value = getattr(left, k)
        if isinstance(right_value, BaseModel) and isinstance(
            left_value, BaseModel
        ):
            if get_config_value(left_value, "frozen"):
                left.__setattr__(k, right_value)
            else:
                merge_models(left_value, right_value)
            continue
        if isinstance(right_value, list):
            links_found = False
            for i in right_value:
                if isinstance(i, Link):
                    links_found = True
                    break
            if links_found:
                continue
            left.__setattr__(k, right_value)
        elif not isinstance(right_value, Link):
            left.__setattr__(k, right_value)

[github-actions]

This issue is stale because it has been open 30 days with no activity.

[martincpt]

That's right. Not only the sync but save, set, update and all methods relying on merge_models ingore Link fields.

I think #653 is related.

This part ignores the field if it's a Link:

elif not isinstance(right_value, Link):
    left.__setattr__(k, right_value)

I also wonder if it was done on purpose. Can anyone answer?