feat: add support for user agent in cloud monitoring source (#1472)

## Description

---
> Add support for user agent in cloud monitoring source
> Make changes to the toolset names to be in sync with the overall
toolbox

## PR Checklist

---
> Thank you for opening a Pull Request! Before submitting your PR, there
are a
> few things you can do to make sure it goes smoothly:

- [x] Make sure you reviewed

[CONTRIBUTING.md](https://github.com/googleapis/genai-toolbox/blob/main/CONTRIBUTING.md)
- [ ] Make sure to open an issue as a

[bug/issue](https://github.com/googleapis/genai-toolbox/issues/new/choose)
before writing your code! That way we can discuss the change, evaluate
  designs, and agree on the general idea
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [x] Appropriate docs were updated (if necessary)
- [] Make sure to add `!` if this involve a breaking change

cmd/root_test.go

@@ -1249,6 +1249,10 @@ func TestPrebuiltTools(t *testing.T) {
 	spannerpg_config, _ := prebuiltconfigs.Get("spanner-postgres")
 	sqlite_config, _ := prebuiltconfigs.Get("sqlite")
 	neo4jconfig, _ := prebuiltconfigs.Get("neo4j")
+	alloydbobsvconfig, _ := prebuiltconfigs.Get("alloydb-postgres-observability")
+	cloudsqlpgobsvconfig, _ := prebuiltconfigs.Get("cloud-sql-postgres-observability")
+	cloudsqlmysqlobsvconfig, _ := prebuiltconfigs.Get("cloud-sql-mysql-observability")
+	cloudsqlmssqlobsvconfig, _ := prebuiltconfigs.Get("cloud-sql-mssql-observability")
 
 	// Set environment variables
 	t.Setenv("API_KEY", "your_api_key")
@@ -1539,6 +1543,46 @@ func TestPrebuiltTools(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "alloydb postgres observability prebuilt tools",
+			in:   alloydbobsvconfig,
+			wantToolset: server.ToolsetConfigs{
+				"alloydb_postgres_cloud_monitoring_tools": tools.ToolsetConfig{
+					Name:      "alloydb_postgres_cloud_monitoring_tools",
+					ToolNames: []string{"get_system_metrics", "get_query_metrics"},
+				},
+			},
+		},
+		{
+			name: "cloudsql postgres observability prebuilt tools",
+			in:   cloudsqlpgobsvconfig,
+			wantToolset: server.ToolsetConfigs{
+				"cloud_sql_postgres_cloud_monitoring_tools": tools.ToolsetConfig{
+					Name:      "cloud_sql_postgres_cloud_monitoring_tools",
+					ToolNames: []string{"get_system_metrics", "get_query_metrics"},
+				},
+			},
+		},
+		{
+			name: "cloudsql mysql observability prebuilt tools",
+			in:   cloudsqlmysqlobsvconfig,
+			wantToolset: server.ToolsetConfigs{
+				"cloud_sql_mysql_cloud_monitoring_tools": tools.ToolsetConfig{
+					Name:      "cloud_sql_mysql_cloud_monitoring_tools",
+					ToolNames: []string{"get_system_metrics", "get_query_metrics"},
+				},
+			},
+		},
+		{
+			name: "cloudsql mssql observability prebuilt tools",
+			in:   cloudsqlmssqlobsvconfig,
+			wantToolset: server.ToolsetConfigs{
+				"cloud_sql_mssql_cloud_monitoring_tools": tools.ToolsetConfig{
+					Name:      "cloud_sql_mssql_cloud_monitoring_tools",
+					ToolNames: []string{"get_system_metrics"},
+				},
+			},
+		},
 	}
 
 	for _, tc := range tcs {

internal/prebuiltconfigs/tools/cloud-sql-mssql-observability.yaml

@@ -72,5 +72,5 @@ tools:
       32. `cloudsql.googleapis.com/database/sqlserver/transactions/full_scan_count`: Total number of unrestricted full scans (base-table or full-index). `cloudsql_database`. `database`, `project_id`, `database_id`.
 
 toolsets:
-  cloud-sql-mssql-cloud-monitoring-tools:
-    - get_system_metrics
+  cloud_sql_mssql_cloud_monitoring_tools:
+    - get_system_metrics

internal/prebuiltconfigs/tools/cloud-sql-mysql-observability.yaml

@@ -106,6 +106,6 @@ tools:
       18. `dbinsights.googleapis.com/pertag/row_count`: Total number of rows affected during query execution. `cloudsql_instance_database`. `user`, `client_addr`, `action`, `application`, `controller`, `db_driver`, `framework`, `route`, `tag_hash`, `row_status`, `database`, `project_id`, `resource_id`.
 
 toolsets:
-  cloud-sql-mysql-cloud-monitoring-tools:
+  cloud_sql_mysql_cloud_monitoring_tools:
     - get_system_metrics
-    - get_query_metrics
+    - get_query_metrics

internal/prebuiltconfigs/tools/cloud-sql-postgres-observability.yaml

@@ -108,6 +108,6 @@ tools:
       18. `cloudsql.googleapis.com/database/postgresql/insights/pertag/row_count`: The number of retrieved or affected rows since the last sample per tag. `cloudsql_instance_database`. `user`, `client_addr`, `action`, `application`, `controller`, `db_driver`, `framework`, `route`, `tag_hash`, `project_id`, `resource_id`.
 
 toolsets:
-  cloud-sql-postgres-cloud-monitoring-tools:
+  cloud_sql_postgres_cloud_monitoring_tools:
     - get_system_metrics
-    - get_query_metrics
+    - get_query_metrics

internal/sources/cloudmonitoring/cloud_monitoring.go

@@ -29,6 +29,26 @@ import (
 
 const SourceKind string = "cloud-monitoring"
 
+type userAgentRoundTripper struct {
+	userAgent string
+	next      http.RoundTripper
+}
+
+func (rt *userAgentRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	newReq := *req
+	newReq.Header = make(http.Header)
+	for k, v := range req.Header {
+		newReq.Header[k] = v
+	}
+	ua := newReq.Header.Get("User-Agent")
+	if ua == "" {
+		newReq.Header.Set("User-Agent", rt.userAgent)
+	} else {
+		newReq.Header.Set("User-Agent", ua+" "+rt.userAgent)
+	}
+	return rt.next.RoundTrip(&newReq)
+}
+
 // validate interface
 var _ sources.SourceConfig = Config{}
 
@@ -65,14 +85,24 @@ func (r Config) Initialize(ctx context.Context, tracer trace.Tracer) (sources.So
 
 	var client *http.Client
 	if r.UseClientOAuth {
-		client = nil
+		client = &http.Client{
+			Transport: &userAgentRoundTripper{
+				userAgent: ua,
+				next:      http.DefaultTransport,
+			},
+		}
 	} else {
 		// Use Application Default Credentials
 		creds, err := google.FindDefaultCredentials(ctx, monitoring.MonitoringScope)
 		if err != nil {
 			return nil, fmt.Errorf("failed to find default credentials: %w", err)
 		}
-		client = oauth2.NewClient(ctx, creds.TokenSource)
+		baseClient := oauth2.NewClient(ctx, creds.TokenSource)
+		baseClient.Transport = &userAgentRoundTripper{
+			userAgent: ua,
+			next:      baseClient.Transport,
+		}
+		client = baseClient
 	}
 
 	s := &Source{