[5302] Added comment in the https example that it is for testing purposes.

doc/examples/https/nginx/kea-nginx.conf

@@ -5,7 +5,12 @@
 #   must generate server certificate and private key as well as
 #   the certifiate authority (CA). The clients' certificates must
 #   be signed by the CA.
-
+#
+#   Note that the steps provided below to generate and setup certifcates
+#   are provided as an example for testing purposes only. Always
+#   consider best known security measures to protect your production
+#   environment.
+#
 #   The server certificate and key can be generated as follows:
 #
 #   openssl genrsa -des3 -out kea-proxy.key 4096