ID conventions in API

We want to move to a more standardized convention for ID element names throughout our APIs. We should move to using collection_instance.id in response/request JSON payloads, as opposed to things like collection_instance.clientid, etc..

So, in /v2015/clients/{clientid} GET

"client": { "clientId": "8547a63e-4659-412f-b5fa-200e03b62ae8",

would become

"client": { "id": "8547a63e-4659-412f-b5fa-200e03b62ae8",