document.NoSerde is not checked for nesteted types.

[skmcgrail]

When marshalling a Go type to a document type it was discovered that the document.IsNoSerde check to determine whether a type is a generated Go type defined in the Smithy model only validates the passed in shape. In this updated test snippet below, it is shown that a custom user defined Go type using a generated type as a field does not correctly prevent usage of the generated type.

func TestNewEncoderUnsupportedTypes(t *testing.T) {
	type customTime time.Time
	type noSerde = document.NoSerde
	type NestedThing struct {
		SomeThing string
		noSerde
	}
	type Thing struct {
		OtherThing  string
		NestedThing NestedThing
	}

	cases := []interface{}{
		time.Now().UTC(),
		customTime(time.Now().UTC()),
		Thing{OtherThing: "cool", NestedThing: NestedThing{SomeThing: "thing"}},
	}

	encoder := json.NewEncoder()
	for _, tt := range cases {
		_, err := encoder.Encode(tt)
		if err == nil {
			t.Errorf("expect error, got nil")
		}
	}
}

IsNoSerde check should be validated for any type that is nested. So usages in fields, or as slice types, or map types etc.