static async checkAssignableRole (req, res, next) {
    const role = req.body.roleId;
    if (role != null && !(await req.user.getAssignableRoles(req.user.userId)).includes(role)) {
      console.log(`Permission denied to ${req.user.userId} while requesting resource: ${req._parsedUrl.pathname}, for assignment-access to role ${role}`);
      return res.serverError(403, 'You do not have permission to access this resource');
    }
    next();
  }
Fails request if a roleId is given in the body, but the user is not a roleAssigner for the given role