Updated docs for secure channels

Author: vmagamedov

docs/client.rst

@@ -59,13 +59,31 @@ Here is how to establish a secure connection to a public gRPC server:
 
 In this case ``grpclib`` uses system CA certificates. But ``grpclib`` has also
 a built-in support for a certifi_ package which contains actual Mozilla's
-collection of CA certificates. All you need is to install it and keep it
-updated -- this is a more favorable way than relying on system CA certificates:
+collection of CA certificates. All you need is to install it and keep it up to
+date -- this is a more favorable way than relying on system CA certificates:
 
 .. code-block:: console
 
   $ pip3 install certifi
 
+Another way to tell which CA certificates to use is by using
+:py:func:`python:ssl.get_default_verify_paths` function:
+
+.. code-block:: python
+
+  channel = Channel(host, port, ssl=ssl.get_default_verify_paths())
+                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This function also supports reading ``SSL_CERT_FILE`` and ``SSL_CERT_DIR``
+environment variables to override your system defaults. It returns
+``DefaultVerifyPaths`` named tuple structure which you can customize and provide
+your own ``cafile`` and ``capath`` values without using environment variables or
+placing certificates into a distribution-specific directory:
+
+.. code-block:: python3
+
+  ssl.get_default_verify_paths()._replace(cafile=YOUR_CA_FILE)
+
 ``grpclib`` also allows you to use a custom SSL configuration by providing a
 :py:class:`~python:ssl.SSLContext` object. We have a simple mTLS auth example
 in our code repository to illustrate how this works.

grpclib/client.py

@@ -645,8 +645,8 @@ def __init__(
             ``ProtoStatusDetailsCodec`` is used by default
 
         :param ssl: ``True`` or :py:class:`~python:ssl.SSLContext` object or
-            :py:class:`~python:ssl.DefaultVerifyPaths` object; if ``True``,
-            default SSL context is used.
+            ``ssl.DefaultVerifyPaths`` object; if ``True``, default SSL context
+            is used.
         """
         if path is not None and (host is not None or port is not None):
             raise ValueError("The 'path' parameter can not be used with the "