fix: don't render topic/timestamp to the ua

Author: pjenvey

src/protocol.rs

@@ -138,8 +138,9 @@ pub struct Notification {
     pub version: String,
     #[serde(default = "default_ttl", skip_serializing)]
     pub ttl: u64,
-    #[serde(skip_serializing_if = "Option::is_none")]
+    #[serde(skip_serializing)]
     pub topic: Option<String>,
+    #[serde(skip_serializing)]
     pub timestamp: u64,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub data: Option<String>,