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/docvalue_field.go

@@ -0,0 +1,42 @@
+// 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
+
+// DocvalueField represents a docvalue field, its name and
+// its format (optional).
+type DocvalueField struct {
+	Field  string
+	Format string
+}
+
+// Source serializes the DocvalueField into JSON.
+func (d DocvalueField) Source() (interface{}, error) {
+	if d.Format == "" {
+		return d.Field, nil
+	}
+	return map[string]interface{}{
+		"field":  d.Field,
+		"format": d.Format,
+	}, nil
+}
+
+// DocvalueFields is a slice of DocvalueField instances.
+type DocvalueFields []DocvalueField
+
+// Source serializes the DocvalueFields into JSON.
+func (d DocvalueFields) Source() (interface{}, error) {
+	if d == nil {
+		return nil, nil
+	}
+	v := make([]interface{}, 0)
+	for _, f := range d {
+		src, err := f.Source()
+		if err != nil {
+			return nil, err
+		}
+		v = append(v, src)
+	}
+	return v, nil
+}