chore: set root_key for NodesFetcher

ic-agent/src/agent/http_transport/dynamic_routing/dynamic_route_provider.rs

@@ -103,6 +103,7 @@ impl<S> DynamicRouteProviderBuilder<S> {
         let fetcher = Arc::new(NodesFetcher::new(
             http_client.clone(),
             Principal::from_text(MAINNET_ROOT_SUBNET_ID).unwrap(),
+            None,
         ));
         let checker = Arc::new(HealthChecker::new(http_client, HEALTH_CHECK_TIMEOUT));
         Self {

ic-agent/src/agent/http_transport/dynamic_routing/nodes_fetch.rs

@@ -36,14 +36,18 @@ pub trait Fetch: Sync + Send + Debug {
 pub struct NodesFetcher {
     http_client: Client,
     subnet_id: Principal,
+    // By default, the nodes fetcher is configured to talk to the mainnet of Internet Computer, and verifies responses using a hard-coded public key.
+    // However, for testnets one can set up a custom public key.
+    root_key: Option<Vec<u8>>,
 }
 
 impl NodesFetcher {
     /// Creates a new `NodesFetcher` instance.
-    pub fn new(http_client: Client, subnet_id: Principal) -> Self {
+    pub fn new(http_client: Client, subnet_id: Principal, root_key: Option<Vec<u8>>) -> Self {
         Self {
             http_client,
             subnet_id,
+            root_key,
         }
     }
 }
@@ -65,6 +69,9 @@ impl Fetch for NodesFetcher {
                     "Failed to build the agent: {err}"
                 ))
             })?;
+        if let Some(key) = self.root_key.clone() {
+            agent.set_root_key(key);
+        }
         let api_bns = agent
             .fetch_api_boundary_nodes_by_subnet_id(self.subnet_id)
             .await