Update to Federation 2 (#632)

Author: smyrick

resources/definitions/Federation.graphql

@@ -1,24 +1,47 @@
-# https://www.apollographql.com/docs/federation/federation-spec/#federation-schema-specification
-scalar _Any
-scalar _FieldSet
+# https://www.apollographql.com/docs/federation/subgraph-spec/
 
 # a union of all types that use the @key directive
 union _Entity
 
+scalar _Any
+scalar FieldSet
+scalar link__Import
+
+enum link__Purpose {
+  """
+  `SECURITY` features provide metadata necessary to securely resolve fields.
+  """
+  SECURITY
+
+  """
+  `EXECUTION` features provide metadata necessary for operation execution.
+  """
+  EXECUTION
+}
+
 type _Service {
-    sdl: String
+  sdl: String!
 }
 
 extend type Query {
-    _entities(representations: [_Any!]!): [_Entity]!
-    _service: _Service!
+  _entities(representations: [_Any!]!): [_Entity]!
+  _service: _Service!
 }
 
-directive @external on FIELD_DEFINITION
-directive @requires(fields: _FieldSet!) on FIELD_DEFINITION
-directive @provides(fields: _FieldSet!) on FIELD_DEFINITION
-directive @key(fields: _FieldSet!) repeatable on OBJECT | INTERFACE
+directive @external on FIELD_DEFINITION | OBJECT
+directive @requires(fields: FieldSet!) on FIELD_DEFINITION
+directive @provides(fields: FieldSet!) on FIELD_DEFINITION
+directive @key(fields: FieldSet!, resolvable: Boolean = true) repeatable on OBJECT | INTERFACE
+directive @link(url: String!, as: String, for: link__Purpose, import: [link__Import]) repeatable on SCHEMA
+directive @shareable repeatable on OBJECT | FIELD_DEFINITION
+directive @inaccessible on FIELD_DEFINITION | OBJECT | INTERFACE | UNION | ARGUMENT_DEFINITION | SCALAR | ENUM | ENUM_VALUE | INPUT_OBJECT | INPUT_FIELD_DEFINITION
+directive @tag(name: String!) repeatable on FIELD_DEFINITION | INTERFACE | OBJECT | UNION | ARGUMENT_DEFINITION | SCALAR | ENUM | ENUM_VALUE | INPUT_OBJECT | INPUT_FIELD_DEFINITION
+directive @override(from: String!) on FIELD_DEFINITION
+directive @composeDirective(name: String!) repeatable on SCHEMA
 
+# This definition is required only for libraries that don't support
+# GraphQL's built-in `extend` keyword
+#
 # `repeatable` is technically not part of the spec, but is added here so that multiple `type Query @extends { ... }`
 # definitions from different DGS schemas would pass validation
 directive @extends repeatable on OBJECT | INTERFACE