message: added test for duplicate field added to card
diff: @@ -1234,6 +1234,12 @@ module("Unit | Service | data", function () {
  assert.throws(() => card.moveField(field, 0), /card is in the embedded format/);
  });
  + test("it throws an error if you name a field with the same name as another field in the card", async function (assert) {
  + let service = this.owner.lookup('service:data');
  + let card = await service.getCard(card1Id, 'isolated');
  + assert.throws(() => card.addField({ name: 'title', type: '@cardstack/core-types::string' }), /field 'fields\/title' which already exists for this card/);
  + });
  +
  test("it throws an error if you try to setNeededWhenEmbedded on an embedded card", async function (assert) {
  let service = this.owner.lookup('service:data');
  let card = await service.getCard(card1Id, 'embedded');
  