Issue search support elasticsearch (#9428)

* Issue search support elasticsearch

* Fix lint

* Add indexer name on app.ini

* add a warnning on SearchIssuesByKeyword

* improve code

vendor/github.com/olivere/elastic/v7/decoder.go

@@ -0,0 +1,38 @@
+// Copyright 2012-present Oliver Eilhard. All rights reserved.
+// Use of this source code is governed by a MIT-license.
+// See http://olivere.mit-license.org/license.txt for details.
+
+package elastic
+
+import (
+	"bytes"
+	"encoding/json"
+)
+
+// Decoder is used to decode responses from Elasticsearch.
+// Users of elastic can implement their own marshaler for advanced purposes
+// and set them per Client (see SetDecoder). If none is specified,
+// DefaultDecoder is used.
+type Decoder interface {
+	Decode(data []byte, v interface{}) error
+}
+
+// DefaultDecoder uses json.Unmarshal from the Go standard library
+// to decode JSON data.
+type DefaultDecoder struct{}
+
+// Decode decodes with json.Unmarshal from the Go standard library.
+func (u *DefaultDecoder) Decode(data []byte, v interface{}) error {
+	return json.Unmarshal(data, v)
+}
+
+// NumberDecoder uses json.NewDecoder, with UseNumber() enabled, from
+// the Go standard library to decode JSON data.
+type NumberDecoder struct{}
+
+// Decode decodes with json.Unmarshal from the Go standard library.
+func (u *NumberDecoder) Decode(data []byte, v interface{}) error {
+	dec := json.NewDecoder(bytes.NewReader(data))
+	dec.UseNumber()
+	return dec.Decode(v)
+}