You may wish to have multiple domains that redirect to your site, e.g. to have an extra TLD or to support www. domains. Ghost itself can only ever have one domain pointed at it. This is intentional for SEO purposes, however you can always redirect extra domains to your Ghost install using nginx.
This is a companion discussion topic for the original entry at https://henrywithu.com/solve-ssl-issue-for-nginx-301-redirect/