Expose node's IP address via feed (#491)

* Fix typos

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* core: Extend `feed::LocatedNode` message with optional IP address

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* core: Expose IpAddr from locator task

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* core: Expose CLI flag to handle IP

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* tests: Consider Option<String> for IP address

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* core: Add node's IP directly to the Node's details

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Adjust testing and serialize node's ip address

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* frontend: Propagate IP address for deserialization purposes

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* core: Clarify the CLI flag documentation

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

backend/telemetry_core/src/main.rs

@@ -82,6 +82,9 @@ struct Opts {
     /// How many nodes from third party chains are allowed to connect before we prevent connections from them.
     #[structopt(long, default_value = "1000")]
     max_third_party_nodes: usize,
+    /// Flag to expose the IP addresses of all connected nodes to the feed subscribers.
+    #[structopt(long)]
+    pub expose_node_ips: bool,
 }
 
 fn main() {
@@ -132,6 +135,7 @@ async fn start_server(num_aggregators: usize, opts: Opts) -> anyhow::Result<()>
             max_queue_len: aggregator_queue_len,
             denylist: opts.denylist,
             max_third_party_nodes: opts.max_third_party_nodes,
+            expose_node_ips: opts.expose_node_ips,
         },
     )
     .await?;