Implement APIv4 infrastructure (#5191)

* Implement APIv4 infrastructure

* Update parameter requirement functions per feedback

model/client.go

@@ -40,7 +40,8 @@ const (
 
 	API_URL_SUFFIX_V1 = "/api/v1"
 	API_URL_SUFFIX_V3 = "/api/v3"
-	API_URL_SUFFIX    = API_URL_SUFFIX_V3
+	API_URL_SUFFIX_V4 = "/api/v4"
+	API_URL_SUFFIX    = API_URL_SUFFIX_V4
 )
 
 type Result struct {
@@ -71,7 +72,7 @@ type Client struct {
 // NewClient constructs a new client with convienence methods for talking to
 // the server.
 func NewClient(url string) *Client {
-	return &Client{url, url + API_URL_SUFFIX, &http.Client{}, "", "", "", "", "", ""}
+	return &Client{url, url + API_URL_SUFFIX_V3, &http.Client{}, "", "", "", "", "", ""}
 }
 
 func closeBody(r *http.Response) {