fix(opensearch): Added @timestamp field for opensearch localhost (#5556)

config/vector.yaml

@@ -60,6 +60,7 @@ transforms:
       - plus_1_events
     source: |-
       .timestamp = from_unix_timestamp!(.created_at, unit: "seconds")
+      ."@timestamp" = from_unix_timestamp(.created_at, unit: "seconds") ?? now()
 
   sdk_transformed:
     type: throttle

crates/analytics/src/opensearch.rs

@@ -493,7 +493,7 @@ impl OpenSearchQueryBuilder {
             let range = json!(time_range);
             filter_array.push(json!({
                 "range": {
-                    "timestamp": range
+                    "@timestamp": range
                 }
             }));
         }