fix: Send context to SDL generation / don't cache (#45)

* fix: Send context to SDL generation / don't cache

- Forwards query context during SDL generation
- Removes SDL caching mechanism as visibility rules can change depending
  on the client

* fix: Bump circle

* fix: Add nil default to context

lib/apollo-federation/schema.rb

@@ -47,11 +47,9 @@ def to_graphql
         super
       end
 
-      def federation_sdl
-        @federation_sdl ||= begin
-          document_from_schema = FederatedDocumentFromSchemaDefinition.new(self)
-          GraphQL::Language::Printer.new.print(document_from_schema.document)
-        end
+      def federation_sdl(context: nil)
+        document_from_schema = FederatedDocumentFromSchemaDefinition.new(self, context: context)
+        GraphQL::Language::Printer.new.print(document_from_schema.document)
       end
     end
   end

lib/apollo-federation/service_field.rb

@@ -10,7 +10,7 @@ module ServiceField
     field(:_service, Service, null: false)
 
     def _service
-      { sdl: context.schema.class.federation_sdl }
+      { sdl: context.schema.class.federation_sdl(context) }
     end
   end
 end