directive @link(url: String!, as: String, import: [Import]) repeatable on SCHEMA

The @link directive links definitions within the document to external schemas.

External schemas are identified by their url, which should end with a specification name and version with the following format: {NAME}/v{MAJOR}.{MINOR}, e.g. url = "https://specs.apollo.dev/federation/v2.5".

External types are associated with the target specification by annotating it with @LinkedSpec meta annotation. External types defined in the specification will be automatically namespaced (prefixed with {NAME}__) unless they are explicitly imported. While both custom namespace (as) and import arguments are optional, due to https://github.com/ExpediaGroup/graphql-kotlin/issues/1830 we currently always require those values to be explicitly provided.