Implement APIv4 infrastructure (#5191)

* Implement APIv4 infrastructure

* Update parameter requirement functions per feedback

api/api.go

@@ -67,7 +67,7 @@ func InitRouter() {
 func InitApi() {
 	BaseRoutes = &Routes{}
 	BaseRoutes.Root = app.Srv.Router
-	BaseRoutes.ApiRoot = app.Srv.Router.PathPrefix(model.API_URL_SUFFIX).Subrouter()
+	BaseRoutes.ApiRoot = app.Srv.Router.PathPrefix(model.API_URL_SUFFIX_V3).Subrouter()
 	BaseRoutes.Users = BaseRoutes.ApiRoot.PathPrefix("/users").Subrouter()
 	BaseRoutes.NeedUser = BaseRoutes.Users.PathPrefix("/{user_id:[A-Za-z0-9]+}").Subrouter()
 	BaseRoutes.Teams = BaseRoutes.ApiRoot.PathPrefix("/teams").Subrouter()