code: function buildRDSSubnetGroup(numZones = 0, { name = 'RDSSubnetGroup' } = {}) {
    if (numZones < 1) {
      return {};
    }
  
    const subnetIds = [];
    for (let i = 1; i <= numZones; i += 1) {
      subnetIds.push({ Ref: `${DB_SUBNET}Subnet${i}` });
    }
  
    return {
      [name]: {
        Type: 'AWS::RDS::DBSubnetGroup',
        Properties: {
          DBSubnetGroupName: {
            Ref: 'AWS::StackName',
          },
          DBSubnetGroupDescription: {
            Ref: 'AWS::StackName',
          },
          SubnetIds: subnetIds,
        },
      },
    };
  }
docs: Build an RDSubnetGroup for a given number of zones
  
  @param {Number} numZones Number of availability zones
  @param {Objects} params
  @return {Object}