encoding/jsonschema: add metadata field to CRD test case

CRDs often declare the metadata field explicitly but do not
explicitly define its subfields. We add a test case for this,
so we can see the subsequent fix more clearly.

For #3907

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: Id015ed86d09ce892a9ebdc5b20a6e434f1b3b49d
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1214625
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>

Author: rogpeppe

encoding/jsonschema/testdata/txtar/crd_embeddedresource.txtar

@@ -24,6 +24,15 @@
                     "openAPIV3Schema": {
                         "type": "object",
                         "properties": {
+                            "apiVersion": {
+                              "type": "string"
+                            },
+                            "kind": {
+                               "type": "string"
+                            },
+                            "metadata": {
+                              "type": "object"
+                            },
                             "r1": {
                                 "type": "object",
                                 "x-kubernetes-embedded-resource": true,
@@ -46,6 +55,9 @@
     }
 }
 -- out/decode/extract --
+apiVersion?: string
+kind?:       string
+metadata?: {}
 r1?: {
 	_embeddedResource
 	...