Named graphs do not retain id when expanded

[mpoffald]

Expanding a node which contains a @graph key just returns an array containing the expanded contents of the graph. Other top-level keys, such as any @id, are dropped.

For example, both of these expanded nodes should contain an :id of "http://example.com/myGraph":

;;1.
(node {:context {:ex "http://example.com/"
                 :id "@id"
                 :graph "@graph"}
       :id :ex/myGraph
       :graph [{:id :ex/foo
                :ex/bar true}]})
;;=>
[{:idx ["@graph" 0],
  :id "http://example.com/foo",
  "http://example.com/bar"
  {:value true, :type nil, :idx ["@graph" 0 :ex/bar]}}] 

;;2.
(node {"@context" {"ex" "http://example.com/"}
       "@id" "ex:myGraph"
       "@graph" [{"@id" "ex:foo"
                  "ex:bar" true}]})
;;=>
[{:idx ["@graph" 0],
  :id "http://example.com/foo",
  "http://example.com/bar"
  {:value true, :type nil, :idx ["@graph" 0 "ex:bar"]}}] 

Here is the example run through json-ld playground:

[
  {
    "@graph": [
      {
        "@id": "https://example.com/foo",
        "https://example.com/bar": [
          {
            "@value": true
          }
        ]
      }
    ],
    "@id": "https://example.com/myGraph"
  }
]

(json-ld playground link)