code: public List<CountPerProjectPermission> countUsersByProjectPermission(DbSession dbSession, Collection<Long> projectIds) {
      return executeLargeInputs(projectIds, mapper(dbSession)::countUsersByProjectPermission);
    }
docs: Count the number of users per permission for a given list of projects
  
  @param projectIds a non-null list of project ids to filter on. If empty then an empty list is returned.