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/search_terms_lookup.go

@@ -0,0 +1,76 @@
+// 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
+
+// TermsLookup encapsulates the parameters needed to fetch terms.
+//
+// For more details, see
+// https://www.elastic.co/guide/en/elasticsearch/reference/7.0/query-dsl-terms-query.html#query-dsl-terms-lookup.
+type TermsLookup struct {
+	index   string
+	typ     string
+	id      string
+	path    string
+	routing string
+}
+
+// NewTermsLookup creates and initializes a new TermsLookup.
+func NewTermsLookup() *TermsLookup {
+	t := &TermsLookup{}
+	return t
+}
+
+// Index name.
+func (t *TermsLookup) Index(index string) *TermsLookup {
+	t.index = index
+	return t
+}
+
+// Type name.
+//
+// Deprecated: Types are in the process of being removed.
+func (t *TermsLookup) Type(typ string) *TermsLookup {
+	t.typ = typ
+	return t
+}
+
+// Id to look up.
+func (t *TermsLookup) Id(id string) *TermsLookup {
+	t.id = id
+	return t
+}
+
+// Path to use for lookup.
+func (t *TermsLookup) Path(path string) *TermsLookup {
+	t.path = path
+	return t
+}
+
+// Routing value.
+func (t *TermsLookup) Routing(routing string) *TermsLookup {
+	t.routing = routing
+	return t
+}
+
+// Source creates the JSON source of the builder.
+func (t *TermsLookup) Source() (interface{}, error) {
+	src := make(map[string]interface{})
+	if t.index != "" {
+		src["index"] = t.index
+	}
+	if t.typ != "" {
+		src["type"] = t.typ
+	}
+	if t.id != "" {
+		src["id"] = t.id
+	}
+	if t.path != "" {
+		src["path"] = t.path
+	}
+	if t.routing != "" {
+		src["routing"] = t.routing
+	}
+	return src, nil
+}