Add OAuth authentication client for HTTPX (#751)

Co-authored-by: Paul Carleton <paulc@anthropic.com>

src/mcp/shared/_httpx_utils.py

@@ -10,6 +10,7 @@ __all__ = ["create_mcp_http_client"]
 def create_mcp_http_client(
     headers: dict[str, str] | None = None,
     timeout: httpx.Timeout | None = None,
+    auth: httpx.Auth | None = None,
 ) -> httpx.AsyncClient:
     """Create a standardized httpx AsyncClient with MCP defaults.
 
@@ -21,6 +22,7 @@ def create_mcp_http_client(
         headers: Optional headers to include with all requests.
         timeout: Request timeout as httpx.Timeout object.
             Defaults to 30 seconds if not specified.
+        auth: Optional authentication handler.
 
     Returns:
         Configured httpx.AsyncClient instance with MCP defaults.
@@ -43,6 +45,12 @@ def create_mcp_http_client(
         timeout = httpx.Timeout(60.0, read=300.0)
         async with create_mcp_http_client(headers, timeout) as client:
             response = await client.get("/long-request")
+
+        # With authentication
+        from httpx import BasicAuth
+        auth = BasicAuth(username="user", password="pass")
+        async with create_mcp_http_client(headers, timeout, auth) as client:
+            response = await client.get("/protected-endpoint")
     """
     # Set MCP defaults
     kwargs: dict[str, Any] = {
@@ -59,4 +67,8 @@ def create_mcp_http_client(
     if headers is not None:
         kwargs["headers"] = headers
 
+    # Handle authentication
+    if auth is not None:
+        kwargs["auth"] = auth
+
     return httpx.AsyncClient(**kwargs)