fix issue #1728
rename timeToLiveSeconds to timeToLive because the type is Duration.
add test code for ISO-8601 Format and also numeric type
Comment From: jitokim
The reason I changed the name of timeToLiveSeconds without changing its type is,
Using the Duration type allows us to preserve the ISO-8601 format, but its default unit is milliseconds.
To keep the function name (withTimeToLive) and its parameter type (Duration) consistent in the CassandraChatMemoryConfig class.
Comment From: markpollack
Thanks, merged in a7a1804fac2987dd2f34640733a29f94e1b46a9c