Update getting_started (#1224)

There was a missing part about the code verifier.

Co-authored-by: Alan Crosswell <[email protected]>

Author: g-normand

docs/getting_started.rst

@@ -273,6 +273,14 @@ Now let's generate an authentication code grant with PKCE (Proof Key for Code Ex
 
 Take note of ``code_challenge`` since we will include it in the code flow URL. It should look something like ``XRi41b-5yHtTojvCpXFpsLUnmGFz6xR15c3vpPANAvM``.
 
+
+Export ``code_verifier`` value as environment variable, it should be something like:
+
+.. sourcecode:: sh
+
+    export CODE_VERIFIER=N0hHRVk2WDNCUUFPQTIwVDNZWEpFSjI4UElNV1pSTlpRUFBXNTEzU0QzRTMzRE85WDFWTzU2WU9ESw==
+
+
 To start the Authorization code flow go to this `URL`_ which is the same as shown below::
 
     http://127.0.0.1:8000/o/authorize/?response_type=code&code_challenge=XRi41b-5yHtTojvCpXFpsLUnmGFz6xR15c3vpPANAvM&code_challenge_method=S256&client_id=vW1RcAl7Mb0d5gyHNQIAcH110lWoOW2BmWJIero8&redirect_uri=http://127.0.0.1:8000/noexist/callback