Add support for exchanging tokens in Keycloak

Change-Id: Ie5d5bee36ece52aefd035013e8f946b1160e8c58
(cherry picked from commit c0ba66642718e492979b43bad2b2fc1ba9d7a217)
diff --git a/doc/requirements.txt b/doc/requirements.txt
index a2a321f..07d4540 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -5,3 +5,4 @@
 sphinx
 sphinx-autobuild
 sphinx-copybutton
+sphinxcontrib-mermaid