Properly limit listing groups boards in FOSS using the REST API...
This is a follow on to !23432 (merged)
The REST API allows for the querying of group issue boards (https://docs.gitlab.com/ee/api/group_boards.html#list-all-group-issue-boards-in-a-group). Although multiple group issue boards are not available in FOSS, the current API will return all boards.
This can be fixed by using Boards::ListService
, similarly to how we do it in https://gitlab.com/gitlab-org/gitlab/blob/master/app/graphql/resolvers/boards_resolver.rb