feat: add x_handle field to SubnetIdentity

[enduserrr]

Description

Summary

Added an optional x_handle field to SubnetIdentity to enable subnet owners to register their X (twitter) handle on-chain.

Changes

• Modified bittensor/core/chain_data/subnet_identity.py:
  • Added x_handle: Optional[str] = None to the dataclass
  • Updated _from_dict to extract the handle using decoded.get("x_handle").
• Added tests/unit_tests/test_subnet_identity.py:
  • Created a new unit test file to verify parsing logic.
  • Backward Compatibility
  • Used .get("x_handle") instead of direct key access.
    This ensures the SDK does not crash when communicating with older nodes or subnets that have not yet set an X handle (legacy data compatibility).

Tests include:

1. Legacy data (with NO x_handle)
2. New valid data (with x_handle)
3. Explicit None
4. Empty string (with x_handle)
5. Extra fields (forward compatibility)
6. Direct init (constructor test to verify x_handle defaults to None)

[cuteolaf]

There's no field for X links in the Subnet Identity.
You need a chain upgrade first.

[basfroman]

Hey @enduserrr,

1. You have to read https://github.com/opentensor/bittensor/blob/master/contrib/CONTRIBUTING.md
2. If you want to apply this logic to SDK, you want to create issue about adding new field to SubnetIdentity to subtensor repo first

[thewhaleking]

Is this attribute on the chain? I don't see anything for this in the Subtensor repo.

[cuteolaf]

It's not on chain yet.