Should we allow relative server?

[dachrillz]

Currently we allow a server in the open api specification to be a relative path. E.g. https://petstore3.swagger.io/ has such a specification.

However, according to the specification of OpenApi 3 (https://swagger.io/docs/specification/api-host-and-base-path/) the following is stated: "If the server URL is relative, it is resolved against the server where the given OpenApi definition file is hosted..."

I guess we can proceed in three ways,

1. Allow relative server url. This means that one can verify e.g. the petstore3 OpenApi spec.
2. Fail if a relative server is passed to the program. This would nudge people to write proper server urls, but could be annoying.
3. Include an options --spec-source-url so that relative server can be properly expanded.

It probably comes down to how peoeple write their specifications. If relative server urls are common they should be supported in my opinion.