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>

api/openapi.yaml

@@ -4,6 +4,18 @@ info:
   description: Orchard orchestration API
   version: 0.1.0
 paths:
+  /controller/info:
+    get:
+      summary: "Retrieve controller's information"
+      tags:
+        - controller
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#components/schemas/ControllerInfo'
   /service-accounts:
     post:
       summary: "Create a Service Account"
@@ -321,3 +333,13 @@ components:
           type: array
           items:
             type: string
+    ControllerInfo:
+      title: Controller's Information
+      type: object
+      properties:
+        version:
+          type: string
+          description: Version number
+        commit:
+          type: string
+          description: Commit hash