Issue #46: implement Python async client values errors and CLI

clients/python/src/mxgateway/auth.py

@@ -0,0 +1,58 @@
+"""Authentication metadata helpers for MXAccess Gateway clients."""
+
+from collections.abc import Sequence
+from dataclasses import dataclass
+
+AUTHORIZATION_HEADER = "authorization"
+REDACTED = "[redacted]"
+
+
+@dataclass(frozen=True)
+class ApiKey:
+    """API key wrapper that avoids leaking the secret through repr output."""
+
+    value: str
+
+    def __post_init__(self) -> None:
+        if not self.value:
+            raise ValueError("api_key must not be empty")
+
+    def __repr__(self) -> str:
+        return f"{type(self).__name__}({REDACTED!r})"
+
+    def bearer_value(self) -> str:
+        return f"Bearer {self.value}"
+
+
+def auth_metadata(api_key: str | ApiKey | None) -> tuple[tuple[str, str], ...]:
+    """Return gRPC metadata for API key auth."""
+
+    if api_key is None:
+        return ()
+
+    key = api_key.value if isinstance(api_key, ApiKey) else api_key
+    if not key:
+        return ()
+
+    return ((AUTHORIZATION_HEADER, f"Bearer {key}"),)
+
+
+def merge_metadata(
+    api_key: str | ApiKey | None,
+    metadata: Sequence[tuple[str, str]] | None = None,
+) -> tuple[tuple[str, str], ...]:
+    """Merge caller metadata with API key metadata."""
+
+    merged = list(metadata or ())
+    merged.extend(auth_metadata(api_key))
+    return tuple(merged)
+
+
+def redact_secret(text: str, secrets: Sequence[str | None]) -> str:
+    """Replace known secret values with a stable redaction marker."""
+
+    redacted = text
+    for secret in secrets:
+        if secret:
+            redacted = redacted.replace(secret, REDACTED)
+    return redacted