Elasticsearch/Prometheus: Set correct service namespace for SigV4 (#39439) (#39652)

Makes sure to set the SigV4 service namespace for Elasticsearch and Prometheus.

Fixes #38440

(cherry picked from commit 45a844e77e)

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

pkg/tsdb/elasticsearch/elasticsearch.go

@@ -84,6 +84,11 @@ func newInstanceSettings() datasource.InstanceFactoryFunc {
 			return nil, fmt.Errorf("error getting http options: %w", err)
 		}
 
+		// Set SigV4 service namespace
+		if httpCliOpts.SigV4 != nil {
+			httpCliOpts.SigV4.Service = "es"
+		}
+
 		version, err := coerceVersion(jsonData["esVersion"])
 
 		if err != nil {

pkg/tsdb/prometheus/prometheus.go

@@ -93,6 +93,11 @@ func newInstanceSettings() datasource.InstanceFactoryFunc {
 			return nil, fmt.Errorf("error getting http options: %w", err)
 		}
 
+		// Set SigV4 service namespace
+		if httpCliOpts.SigV4 != nil {
+			httpCliOpts.SigV4.Service = "aps"
+		}
+
 		httpMethod, ok := jsonData["httpMethod"].(string)
 		if !ok {
 			httpMethod = defaultHttpMethod