hardcode old realm oapi spec into CLI

[cdhanna]

Now that the scala service is no longer hosted, we cannot access the old realms oapi spec; which is causing the beam oapi generate command to fail :(

Here is the old spec file. We should embed this in the CLI as a resource, so that we can use it directly to keep generating the SDK with the old types, so that we don't releasing a breaking change by accident.
realms-docs.json

Today, in the SwaggerService, we have a list of oapi docs we download and they are in 3 formats, protoActor, basic, and object, but we should add 4th which is "legacy file", so that we can re-use this approach in future cases where scala services are deactivated. This legacy thing needs to say if it is emulating a basic or object service, because that is important later in the generation phase.