feat(product-catalog): add DSN-derived attributes to DB telemetry

Extract connection attributes from the DSN (e.g. host, port) using
otelsql.AttributesFromDSN and include them alongside the existing
semconv.DBSystemNamePostgreSQL attribute on both spans and DB stats
metrics. Note: AttributesFromDSN does not yet extract db.namespace
(database name).

Co Authored By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: cyrille-leclerc

src/product-catalog/main.go

@@ -65,9 +65,13 @@ func initDatabase() error {
 		return fmt.Errorf("DB_CONNECTION_STRING environment variable not set")
 	}
 
+	dbAttrs := otelsql.WithAttributes(
+		append(otelsql.AttributesFromDSN(connStr), semconv.DBSystemNamePostgreSQL)...,
+	)
+
 	var err error
 	db, err = otelsql.Open("postgres", connStr,
-		otelsql.WithAttributes(semconv.DBSystemNamePostgreSQL),
+		dbAttrs,
 		otelsql.WithSpanOptions(otelsql.SpanOptions{
 			OmitConnResetSession: true,
 			OmitRows:             true,
@@ -76,7 +80,7 @@ func initDatabase() error {
 		return fmt.Errorf("failed to open database connection: %w", err)
 	}
 
-	reg, err = otelsql.RegisterDBStatsMetrics(db, otelsql.WithAttributes(semconv.DBSystemNamePostgreSQL))
+	reg, err = otelsql.RegisterDBStatsMetrics(db, dbAttrs)
 	if err != nil {
 		return fmt.Errorf("failed to register database metrics: %w", err)
 	}