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_boosting.go

@@ -0,0 +1,97 @@
+// 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
+
+// A boosting query can be used to effectively
+// demote results that match a given query.
+// For more details, see:
+// https://www.elastic.co/guide/en/elasticsearch/reference/7.0/query-dsl-boosting-query.html
+type BoostingQuery struct {
+	Query
+	positiveClause Query
+	negativeClause Query
+	negativeBoost  *float64
+	boost          *float64
+}
+
+// Creates a new boosting query.
+func NewBoostingQuery() *BoostingQuery {
+	return &BoostingQuery{}
+}
+
+func (q *BoostingQuery) Positive(positive Query) *BoostingQuery {
+	q.positiveClause = positive
+	return q
+}
+
+func (q *BoostingQuery) Negative(negative Query) *BoostingQuery {
+	q.negativeClause = negative
+	return q
+}
+
+func (q *BoostingQuery) NegativeBoost(negativeBoost float64) *BoostingQuery {
+	q.negativeBoost = &negativeBoost
+	return q
+}
+
+func (q *BoostingQuery) Boost(boost float64) *BoostingQuery {
+	q.boost = &boost
+	return q
+}
+
+// Creates the query source for the boosting query.
+func (q *BoostingQuery) Source() (interface{}, error) {
+	// {
+	//     "boosting" : {
+	//         "positive" : {
+	//             "term" : {
+	//                 "field1" : "value1"
+	//             }
+	//         },
+	//         "negative" : {
+	//             "term" : {
+	//                 "field2" : "value2"
+	//             }
+	//         },
+	//         "negative_boost" : 0.2
+	//     }
+	// }
+
+	query := make(map[string]interface{})
+
+	boostingClause := make(map[string]interface{})
+	query["boosting"] = boostingClause
+
+	// Negative and positive clause as well as negative boost
+	// are mandatory in the Java client.
+
+	// positive
+	if q.positiveClause != nil {
+		src, err := q.positiveClause.Source()
+		if err != nil {
+			return nil, err
+		}
+		boostingClause["positive"] = src
+	}
+
+	// negative
+	if q.negativeClause != nil {
+		src, err := q.negativeClause.Source()
+		if err != nil {
+			return nil, err
+		}
+		boostingClause["negative"] = src
+	}
+
+	if q.negativeBoost != nil {
+		boostingClause["negative_boost"] = *q.negativeBoost
+	}
+
+	if q.boost != nil {
+		boostingClause["boost"] = *q.boost
+	}
+
+	return query, nil
+}