Classes decorated with @strawberry.scalar do not allow classmethods of the class to be used at runtime.

Consider as an example the scalar:

@strawberry.scalar
class Timestamp(int):
    """An int representing the number of seconds before or after 1970-01-01-T00:00Z."""

    @classmethod
    def from_optional(cls, value: Optional[int]) -> Optional[Timestamp]:
        return None if value is None else cls(value)

And related schema definition:

@strawberry.type
class MyData:
    def start_time(self, t: Optional[int]) -> Optional[Timestamp]:
        return Timestamp.from_optional(t)

Resolving the start_time field will fail with the error
ERROR strawberry.execution:execute.py:249 'ScalarWrapper' object has no attribute 'from_optional'.

It seems like ScalarWrapper does not preserve all relevant attributes of the wrapped class. I have observed that another common class wrapper @strawberry.type does preserve classmethods correctly.