import json

class DataContractRegistry:
    def __init__(self):
        self._contracts = {}

    def register(self, name: str, schema: dict, version: int = 1):
        # Store contract with versioning and associated schema
        self._contracts[name] = {
            "version": version,
            "schema": schema,
        }

    def get(self, name: str):
        return self._contracts.get(name)

    def list_contracts(self):
        return {k: v for k, v in self._contracts.items()}

    def conform(self, name: str, payload: dict) -> bool:
        """Basic conformance check for a given payload against a registered contract.

        If a contract is registered with a 'fields' list inside its schema, we
        require that all those fields exist in the payload. Extra fields are
        allowed for forward-compatibility.
        """
        contract = self._contracts.get(name)
        if not contract:
            # No contract defined; be permissive in MVP
            return True
        schema = contract.get("schema", {})
        if isinstance(schema, dict) and "fields" in schema:
            required = set(schema["fields"])
            return required.issubset(set(payload.keys()))
        # Fallback: no strict contract; assume conformant
        return True