[MM-24453] Sanitize user term search (#14494)

* Sanitize user term search

Remove the @ at the beginning of the search term in order to
make it possible for ES to return results

store/searchlayer/user_layer.go

@@ -45,7 +45,9 @@ func (s *SearchUserStore) Search(teamId, term string, options *model.UserSearchO
 				return []*model.User{}, nil
 			}
 
-			usersIds, err := engine.SearchUsersInTeam(teamId, listOfAllowedChannels, term, options)
+			sanitizedTerm := sanitizeSearchTerm(term)
+
+			usersIds, err := engine.SearchUsersInTeam(teamId, listOfAllowedChannels, sanitizedTerm, options)
 			if err != nil {
 				mlog.Error("Encountered error on Search", mlog.String("search_engine", engine.GetName()), mlog.Err(err))
 				continue
@@ -101,10 +103,11 @@ func (s *SearchUserStore) autocompleteUsersInChannelByEngine(engine searchengine
 	var err *model.AppError
 	uchanIds := []string{}
 	nuchanIds := []string{}
+	sanitizedTerm := sanitizeSearchTerm(term)
 	if options.ListOfAllowedChannels != nil && !strings.Contains(strings.Join(options.ListOfAllowedChannels, "."), channelId) {
-		nuchanIds, err = engine.SearchUsersInTeam(teamId, options.ListOfAllowedChannels, term, options)
+		nuchanIds, err = engine.SearchUsersInTeam(teamId, options.ListOfAllowedChannels, sanitizedTerm, options)
 	} else {
-		uchanIds, nuchanIds, err = engine.SearchUsersInChannel(teamId, channelId, options.ListOfAllowedChannels, term, options)
+		uchanIds, nuchanIds, err = engine.SearchUsersInChannel(teamId, channelId, options.ListOfAllowedChannels, sanitizedTerm, options)
 	}
 	if err != nil {
 		return nil, err

store/searchlayer/utils.go

@@ -0,0 +1,10 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package searchlayer
+
+import "strings"
+
+func sanitizeSearchTerm(term string) string {
+	return strings.TrimLeft(term, "@")
+}

store/searchtest/user_layer.go

@@ -104,7 +104,7 @@ var searchUserStoreTests = []searchTest{
 	{
 		Name: "Should ignore leading @ when searching users",
 		Fn:   testShouldIgnoreLeadingAtSymbols,
-		Tags: []string{ENGINE_MYSQL, ENGINE_POSTGRES},
+		Tags: []string{ENGINE_ALL},
 	},
 	{
 		Name: "Should search users in a case insensitive manner",