startup notification: create_dir_all parent dir, add context for io ops

magic-nix-cache/src/main.rs

@@ -392,8 +392,33 @@ async fn main_cli() -> Result<()> {
 
         tracing::debug!("Startup notification via file at {startup_notification_file_path:?}");
 
-        let mut notification_file = File::create(&startup_notification_file_path).await?;
-        notification_file.write_all(file_contents).await?;
+        if let Some(parent_dir) = startup_notification_file_path.parent() {
+            tokio::fs::create_dir_all(parent_dir)
+                .await
+                .with_context(|| {
+                    format!(
+                        "failed to create parent directory for startup notification file path: {}",
+                        startup_notification_file_path.display()
+                    )
+                })?;
+        }
+        let mut notification_file = File::create(&startup_notification_file_path)
+            .await
+            .with_context(|| {
+                format!(
+                    "failed to create startup notification file to path: {}",
+                    startup_notification_file_path.display()
+                )
+            })?;
+        notification_file
+            .write_all(file_contents)
+            .await
+            .with_context(|| {
+                format!(
+                    "failed to write startup notification file to path: {}",
+                    startup_notification_file_path.display()
+                )
+            })?;
 
         tracing::debug!("Created startup notification file at {startup_notification_file_path:?}");
     }