domain 

(OPTIONAL)
Make your application available via HTTP through port 80 (the HTTP default port) under a free my-domain.sloppy.zone or a custom domain name. Learn more about how to configure internal and external domains for your applications. Example:

"domain": { "uri": "my-domain.sloppy.zone" }

When using a docker-compose.yml, domainname is mapped to domain.uri, specifying the domain name:

domainname: my-domain.sloppy.zone

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