Add search client for OpenSearch to log and query API events

Related to #5 (closed) This branch only for writing. Query in next follow up change...

config/struct.go

@@ -24,7 +24,15 @@ func Load(prefix string, configPtr interface{}) error {
 		return errors.Errorf("%T is not &struct", configPtr)
 	}
 	v := reflect.ValueOf(configPtr)
-	return load(prefix, t.Elem(), v.Elem())
+	if err := load(prefix, t.Elem(), v.Elem()); err != nil {
+		return errors.Wrapf(err, "failed to load config with prefix %s", prefix)
+	}
+	if validator, ok := configPtr.(Validator); ok {
+		if err := validator.Validate(); err != nil {
+			return errors.Wrapf(err, "invalid config with prefix %s", prefix)
+		}
+	}
+	return nil
 }
 
 type nameValue struct {