update to appropriately write lists out to the vault secret object

[kmcgovern-apixio]

Currently when you attempt to write out a list as a value into vault the writer will incorrectly format the list

example

{
   "key": "[value1, value2]"
}

This is fairly annoying and can be worked-around but it's not the behavior I was expecting. My work-around for this currently is just to use a comma-separated list but it's not ideal. Explicitly using a JsonArray object works but then I have issues when using jackson to convert objects and need special work-arounds just for writing a map to vault.

This change will convert any list objects intoJsonArray objects to make using this library a bit simpler and straight foward. I didn't see any tests for the Logical class so i made a quick unit test to show it's working. I've tested this locally for my user-case and it seems to do the trick.

[ianferguson]

👋 sorry I missed this when you opened it -- at this point I'm not planning on maintaining this library or working on adding additional changes beyond the X-Vault-Request header support that was added when this forked from the upstream https://github.com/bettercloud/vault-java-driver