MM-25263 Add group members to search and get users and create getGroupStats endpoint (#14733)

Add tests for SearchInGroup

store/store.go

@@ -322,6 +322,7 @@ type UserStore interface {
 	SearchInChannel(channelId string, term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
 	SearchNotInChannel(teamId string, channelId string, term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
 	SearchWithoutTeam(term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
+	SearchInGroup(groupID string, term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
 	AnalyticsGetInactiveUsersCount() (int64, *model.AppError)
 	AnalyticsGetSystemAdminCount() (int64, *model.AppError)
 	AnalyticsGetGuestCount() (int64, *model.AppError)