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/uritemplates/utils.go

@@ -0,0 +1,13 @@
+package uritemplates
+
+func Expand(path string, expansions map[string]string) (string, error) {
+	template, err := Parse(path)
+	if err != nil {
+		return "", err
+	}
+	values := make(map[string]interface{})
+	for k, v := range expansions {
+		values[k] = v
+	}
+	return template.Expand(values)
+}