add draft for dke:ping command

.node-version

@@ -0,0 +1 @@
+16

modules/ROOT/pages/ar2/testing.adoc

@@ -65,7 +65,7 @@ Additionally, the public key used for signing the authorize redirect needs to be
 * Onboard the application:
 ** If your application provide an easy way to onboard an endpoint this should be the preferred way
 ** Onboard manually using the authorize page:
-** Go to: http://app.qa.agrirouter.farm/en/application/{YOUR_APP_ID}/authorize?response_type=onboard&redirect_uri={YOUR_REDIRECT_URL}
+** Go to: http://app.qa.agrirouter.farm/en/application/\{YOUR_APP_ID\}/authorize?response_type=onboard&redirect_uri=\{YOUR_REDIRECT_URL\}
 ** Click on `connect`
 ** Your application should appear in the office column of your farmer page
 ** If you need a way to send messages to your application you could use the IO Tool

modules/ROOT/pages/commands/endpoint.adoc

@@ -4,6 +4,47 @@
 
 This chapter will list all messages to tell the agrirouter, what the endpoint is capable of, who it is and what it wants to receive.
 
+== Ping Command
+
+=== Definition
+
+The ping command is used to check if the endpoint still exists and to know whether agrirouter correctly processes messages.
+
+This is mainly useful when using an MQTT router device, to recognize if an endpoint has been deleted by the user from the agrirouter UI. All other cases can be known to the application itself.
+
+=== Command
+
+[cols=","]
+|==================================
+|Command |dke:ping
+|Protobuf Schema | -
+|TypeURL | -
+|==================================
+
+No parameters are needed.
+
+=== Result
+
+[cols="1,2,2"]
+|=================================================================================
+|           | Case 1 | Case 2
+|ResultCode |ACK | ACK_WITH_FAILURE
+|Protobuf Schema | - | agrirouter.commons.Messages
+|TypeURL | - | types.agrirouter.com/agrirouter.commons.Messages
+|=================================================================================
+
+The result is a simple `ACK` (accompanied with `response_code == 200`) or an `ACK_WITH_FAILURE` (`response_code == 404`).
+
+==== ACK
+
+Receiving an `ACK` means that the endpoint exists.
+
+==== ACK_WITH_FAILURE
+
+Receiving an `ACK_WITH_FAILURE` means that the endpoint has recently been deleted. You must remove this endpoint from your endpoints list.
+
+
+
 == Capabilities Command
 
 === Definition
@@ -20,11 +61,11 @@ The list of technical message types can include any TechnicalMessageFormat menti
 === Command
 
 [cols=",",]
-|=====================================================================================
+|=================================================================================
 |Command |dke:capabilities
 |Protobuf Schema |agrirouter.request.payload.endpoint.CapabilitySpecification
 |TypeURL |types.agrirouter.com/agrirouter.request.payload.endpoint.CapabilitySpecification
-|=====================================================================================
+|=================================================================================
 
 Parameters are the following elements: