add OIDCRedisCacheUsername to auth_openidc.conf docs
# When not specified, no authentication is performed.
#OIDCRedisCachePassword <password>
+# Username to be used if the Redis server requires authentication: http://redis.io/commands/auth
+# NB: this can only used with Redis 6 (ACLs) or later
+# When not specified, the implicit user "default" is used
+#OIDCRedisCacheUsername <username>
+
# Logical database to select on the Redis server: https://redis.io/commands/select
# When not defined the default database 0 is used.
#OIDCRedisCacheDatabase <number>
