Controller info endpoint and API integration examples (#75)

* Controller API: introduce controller's information endpoint

* Prevent generation of empty events after channel closure

* Allow events to be buffered in the events channel

* Controller API: introduce controller's information endpoint[1]

* IntegrationGuide.md: a couple of Python and Golang examples

* Rephrase a sentence

Co-authored-by: Fedor Korotkov <fedor.korotkov@gmail.com>

---------

Co-authored-by: Fedor Korotkov <fedor.korotkov@gmail.com>

pkg/client/controller.go

@@ -0,0 +1,23 @@
+package client
+
+import (
+	"context"
+	v1 "github.com/cirruslabs/orchard/pkg/resource/v1"
+	"net/http"
+)
+
+type ControllerService struct {
+	client *Client
+}
+
+func (service *ControllerService) Info(ctx context.Context) (v1.ControllerInfo, error) {
+	var controllerInfo v1.ControllerInfo
+
+	err := service.client.request(ctx, http.MethodGet, "controller/info", nil, &controllerInfo,
+		nil)
+	if err != nil {
+		return controllerInfo, err
+	}
+
+	return controllerInfo, nil
+}