Fix KVGetResult scheme to match Consul API

[ppressives]

Actually Value field in Consul API is optional and deserialization fails if key value is null.

curl -X PUT localhost:8500/v1/kv/foo/
true
curl localhost:8500/v1/kv/foo/

[
    {
        "LockIndex": 0,
        "Key": "foo/",
        "Flags": 0,
        "Value": null,
        "CreateIndex": 21,
        "ModifyIndex": 21
    }
]

[ppressives]

@rossabaker

[rossabaker]

Apologies for the slow response. I took a vacation, and then my motherboard took a vacation after that.

[rossabaker]

This is going to be a binary breaking change and require another major version, though I can't think of a better way. It would probably be incorrect and/or evil to conflate the empty string with a null value here.

@aldiyen, do you have any thoughts here?

[aldiyen]

Heh interesting, the Consul documentation doesn't seem to say anything about that. I cannot think of any better alternative either.

I think either kvGetRaw or kvGetJson needs to change as well to handle the null value in Consul's KV store situation, as I suspect that kvGetRaw will return Some(Array()) and then the JSON parsing will blow up, which seems more confusing than having kvGetJson spit out a None. I haven't tested this theory though.

[ppressives]

You are absolutely right. Corrected this case.

[aldiyen]

This looks like it'll work to me.

[rossabaker]

I feel terrible for the delay on this. Please don't hesitate to give me a nudge if I'm this unresponsive.