Websocket bootstrap subscription & attempt ID (#211)

* Websocket bootstrap subscription & attempt ID

* available since v21.0

* Update websockets.md

docs/commands/rpc-protocol.md

@@ -908,6 +908,10 @@ Initialize bootstrap to specific **IP address** and **port**. Not compatible wit
 _version 20.0+_  
 Default "false". If "true", frontier confirmation will not be performed for this bootstrap. Normally not to be changed.
 
+**Optional "id"**  
+_version 21.0+_  
+String, empty by default. Set specific ID for new bootstrap attempt for better tracking.
+
 ---
 
 ### bootstrap_any  
@@ -929,6 +933,10 @@ Initialize multi-connection bootstrap to random peers. Not compatible with launc
 _version 20.0+_  
 Boolean, false by default. Manually force closing of all current bootstraps  
 
+**Optional "id"**  
+_version 21.0+_  
+String, empty by default. Set specific ID for new bootstrap attempt for better tracking.
+
 ---
 
 ### bootstrap_lazy  
@@ -952,6 +960,10 @@ Initialize lazy bootstrap with given block **hash**. Not compatible with launch
 
 Boolean, false by default. Manually force closing of all current bootstraps  
 
+**Optional "id"**  
+_version 21.0+_  
+String, empty by default. Set specific ID for new bootstrap attempt for better tracking.
+
 ---
 
 ### bootstrap_status  

docs/integration-guides/websockets.md

@@ -496,6 +496,7 @@ Notes:
 - If work generation fails, the notification is similar to the work cancelled notification, except `"reason": "failure"`
 - When work generation is done locally it will show `"source": "local"`
 
+---
 
 ### Node telemetry
 
@@ -589,4 +590,56 @@ No filters are currently available for the `new_unconfirmed_block` topic.
     "subtype": "receive"
   }
 }
-```
+```
+
+---
+
+#### Bootstrap
+
+This subscription is available since _v21.0_
+
+##### Subscribing
+
+To subscribe to bootstrap attempts start/exit notifications:
+```json
+{
+  "action": "subscribe",
+  "topic": "bootstrap"
+}
+```
+
+##### Filtering options
+
+No filters are currently available for the `bootstrap` topic.
+
+##### Sample Results
+
+```json
+{
+  "topic": "bootstrap",
+  "time": "1561661740065",
+  "message": {
+    "reason": "started",
+    "id": "C9FF2347C4DF512A7F6B514CC4A0F79A",
+    "mode": "legacy"
+  }
+}
+```
+
+```json
+{
+  "topic": "bootstrap",
+  "time": "1561661740565",
+  "message": {
+    "reason": "exited",
+    "id": "C9FF2347C4DF512A7F6B514CC4A0F79A",
+    "mode": "legacy",
+    "total_blocks": "1000000",
+    "duration": "500"
+  }
+}
+```
+
+Notes:
+
+- The duration is in seconds