Added documentation for current state request

Author: OleksandrChaika

README.md

@@ -69,6 +69,11 @@ MQTT communication is done via 3 MQTT topics:
 |------|  -------- | ----------- |
 | selfupdate/currentstate | OUT | This message is being sent once, on SUA start. It contains information about currently installed OS version.
 
+## selfupdate/currentstate/get
+| Topic| Direction | Description |
+|------|  -------- | ----------- |
+| selfupdate/currentstate/get | IN | This message can be received at any point of time. Indicates that SUA should send back version of installed OS as current state.
+
 ## selfupdate/desiredstatefeedback
 | Topic| Direction | Description |
 |------|  -------- | ----------- |

docs/bfb.md

@@ -24,6 +24,15 @@ MQTT Topic: selfupdate/desiredstate
 }
 ```
 
+## Current state request
+This message is a trigger to send back version of installed OS. Can be received at any point of time.
+```
+{
+    "activityId": "",
+    "timestamp": 123456789
+}
+```
+
 ## Desired state
 
 This message indicates that SUA needs to perform an update operation.

docs/testing/README.md

@@ -67,6 +67,11 @@ mosquitto_sub -t "selfupdate/currentstate"
 mosquitto_sub -t "selfupdate/desiredstatefeedback"
 ```
 
+## Trigger current state request
+```
+mosquitto_pub -t "selfupdate/currentstate/get" -f docs/testing/mqtt/current-state-get.json
+```
+
 # Container
 
 For testing the container variant, it shall be ensured that all the components are connected to the same network and using proper ports mapping, so that they would be able to communicate with each other.