Added json.Controller

[BSick7]

This adds a json.Controller to provide a return-style interaction with APIs.

This is how an API call would differ between Controller and Handler.

Handler

// Endpoint definition
standard.NewEndpoint("GET", "/orgs/{orgName}/stacks/{stackId}/blocks/{blockId}/webhooks", json.Handler(webhooks.List)),

// API Logic
func (wh Webhooks) List(w *json.ResponseWriter, r *json.Request) {
	BlockEndpoint(w, r, func(orgName string, stackId, blockId int64) {
		webhooks, err := wh.notificationClient.GetWebhooks(orgName, stackId, blockId)
		if err != nil {
			log.Printf("unable to get webhooks: %s", err)
			w.SendError(errors.NewApiError(nil))
			return
		}

		w.Send(webhooks)
	})
}

Controller

// Endpoint definition
standard.NewEndpoint("GET", "/orgs/{orgName}/stacks/{stackId}/blocks/{blockId}/webhooks", json.Controller(webhooks.List)),

// API Logic
func (wh Webhooks) List(r *json.Request) ([]models.Webhook, error) {
	orgName, stackId, blockId, err := BlockEndpoint(r)
	if err != nil {
		return nil, err
	}
	return wh.notificationClient.GetWebhooks(orgName, stackId, blockId)
}