message: change type of customDomain to IDomainName
  Additional details:
diff: @@ -68,7 +68,7 @@ export interface ApiRouteProps {
  }
  export interface ApiCustomDomainProps {
  - readonly domainName: string | apig.DomainName;
  + readonly domainName: string | apig.IDomainName;
  readonly hostedZone?: string | route53.HostedZone;
  readonly certificate?: acm.Certificate;
  readonly path?: string;
  