Add timestamp header to builder API block-header request

builder_api/src/api.rs

@@ -1,5 +1,5 @@
 use core::time::Duration;
-use std::sync::Arc;
+use std::{sync::Arc, time::SystemTime};
 
 use anyhow::{bail, ensure, Result};
 use arc_swap::ArcSwap;
@@ -38,6 +38,7 @@ use crate::{
     BuilderApiFormat, BuilderConfig,
 };
 
+const DATE_MS_HEADER: &str = "Date-Milliseconds";
 const REQUEST_TIMEOUT: Duration = Duration::from_secs(BUILDER_PROPOSAL_DELAY_TOLERANCE);
 
 #[derive(Debug, Error)]
@@ -237,6 +238,14 @@ impl Api {
             )
         };
 
+        let request = match SystemTime::now().duration_since(SystemTime::UNIX_EPOCH) {
+            Ok(timestamp) => request.header(DATE_MS_HEADER, format!("{}", timestamp.as_millis())),
+            Err(error) => {
+                debug!("unable to calculate timestamp: {error:?}");
+                request
+            }
+        };
+
         let response = request.send().await?;
         let response = handle_error(response).await?;