Add auth options for RemoteRunnable (#46)

This PR adds support for most authentication scenarios to
`RemoteRunnable`. It does this by exposing auth kwargs available in the
`httpx` clients.

From the [httpx
source](https://github.com/encode/httpx/blob/master/httpx/_client.py#L582):
* **auth** - *(optional)* An authentication class to use when sending
requests.
* **headers** - *(optional)* Dictionary of HTTP headers to include when
sending requests.
* **cookies** - *(optional)* Dictionary of Cookie items to include when
sending requests.
* **verify** - *(optional)* SSL certificates (a.k.a CA bundle) used to
verify the identity of requested hosts. Either `True` (default CA
bundle), a path to an SSL certificate file, an `ssl.SSLContext`, or
`False` (which will disable verification).
* **cert** - *(optional)* An SSL certificate used by the requested host
to authenticate the client. Either a path to an SSL certificate file, or
two-tuple of (certificate file, key file), or a three-tuple of
(certificate file, key file, password).

---------

Co-authored-by: Eugene Yurtsev <[email protected]>

langserve/client.py

@@ -6,6 +6,7 @@
 from typing import (
     Any,
     AsyncIterator,
+    Dict,
     Iterator,
     List,
     Optional,
@@ -15,6 +16,7 @@
 from urllib.parse import urljoin
 
 import httpx
+from httpx._types import AuthTypes, CertTypes, CookieTypes, HeaderTypes, VerifyTypes
 from langchain.callbacks.tracers.log_stream import RunLog, RunLogPatch
 from langchain.load.dump import dumpd
 from langchain.schema.runnable import Runnable
@@ -110,16 +112,48 @@ def __init__(
         url: str,
         *,
         timeout: Optional[float] = None,
+        auth: Optional[AuthTypes] = None,
+        headers: Optional[HeaderTypes] = None,
+        cookies: Optional[CookieTypes] = None,
+        verify: VerifyTypes = True,
+        cert: Optional[CertTypes] = None,
+        client_kwargs: Optional[Dict[str, Any]] = None,
     ) -> None:
         """Initialize the client.
 
         Args:
             url: The url of the server
             timeout: The timeout for requests
+            auth: Authentication class for requests
+            headers: Headers to send with requests
+            cookies: Cookies to send with requests
+            verify: Whether to verify SSL certificates
+            cert: SSL certificate to use for requests
+            client_kwargs: If provided will be unpacked as kwargs to both the sync
+                           and async httpx clients
         """
+        _client_kwargs = client_kwargs or {}
         self.url = url
-        self.sync_client = httpx.Client(base_url=url, timeout=timeout)
-        self.async_client = httpx.AsyncClient(base_url=url, timeout=timeout)
+        self.sync_client = httpx.Client(
+            base_url=url,
+            timeout=timeout,
+            auth=auth,
+            headers=headers,
+            cookies=cookies,
+            verify=verify,
+            cert=cert,
+            **_client_kwargs,
+        )
+        self.async_client = httpx.AsyncClient(
+            base_url=url,
+            timeout=timeout,
+            auth=auth,
+            headers=headers,
+            cookies=cookies,
+            verify=verify,
+            cert=cert,
+            **_client_kwargs,
+        )
 
         # Register cleanup handler once RemoteRunnable is garbage collected
         weakref.finalize(self, _close_clients, self.sync_client, self.async_client)