[BUG] Enum custom signature in 3.14

[ego-thales]

Describe the bug:

Failed test in 3.14:

____________________ test_enum_with_explicit_support_signature ____________________

enum = <enum 'EnumFactory'>

    def test_enum_with_explicit_support_signature(enum):
        """Test our enums signature."""
>       assert repr(signature(enum)) == "<Signature (value)>"
E       AssertionError: assert '<Signature (*values)>' == '<Signature (value)>'
E         
E         - <Signature (value)>
E         + <Signature (*values)>
E         ?             +     +

test/scio/utils/enums/test_enums.py:11: AssertionError

Likely culprit (python/cpython/pull/116234):
https://github.com/python/cpython/blob/5ae4612e72c315ac18edaeee9e4851654844a454/Lib/enum.py#L1087-L1099

How to reproduce:

from enum import Enum
from inspect import Signature, signature

class Foo(int, Enum):
    BAR = 1
    __signature__ = Signature()

>>> # Python 3.14.0
>>> signature(Foo)
<Signature (*values)>

>>> # Python 3.12 and 3.13
>>> signature(Foo)
<Signature ()>

Environment information:

scio version: 1.0.1.dev0
Python version: 3.14.0
Platform: Linux (#85~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Sep 19 16:18:59 UTC 2)
Machine type: x86_64

[ego-thales]

Fixed at the metaclass level.

[ego-thales]

Regression: the fix breaks for python <= 3.13

[ego-thales]

Current fix overrides metaclass __signature__ while keeping the class attribute override (for backwards compatibility).