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_queries_term.go

@@ -0,0 +1,58 @@
+// 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
+
+// TermQuery finds documents that contain the exact term specified
+// in the inverted index.
+//
+// For details, see
+// https://www.elastic.co/guide/en/elasticsearch/reference/7.0/query-dsl-term-query.html
+type TermQuery struct {
+	name      string
+	value     interface{}
+	boost     *float64
+	queryName string
+}
+
+// NewTermQuery creates and initializes a new TermQuery.
+func NewTermQuery(name string, value interface{}) *TermQuery {
+	return &TermQuery{name: name, value: value}
+}
+
+// Boost sets the boost for this query.
+func (q *TermQuery) Boost(boost float64) *TermQuery {
+	q.boost = &boost
+	return q
+}
+
+// QueryName sets the query name for the filter that can be used
+// when searching for matched_filters per hit
+func (q *TermQuery) QueryName(queryName string) *TermQuery {
+	q.queryName = queryName
+	return q
+}
+
+// Source returns JSON for the query.
+func (q *TermQuery) Source() (interface{}, error) {
+	// {"term":{"name":"value"}}
+	source := make(map[string]interface{})
+	tq := make(map[string]interface{})
+	source["term"] = tq
+
+	if q.boost == nil && q.queryName == "" {
+		tq[q.name] = q.value
+	} else {
+		subQ := make(map[string]interface{})
+		subQ["value"] = q.value
+		if q.boost != nil {
+			subQ["boost"] = *q.boost
+		}
+		if q.queryName != "" {
+			subQ["_name"] = q.queryName
+		}
+		tq[q.name] = subQ
+	}
+	return source, nil
+}