`fga store import` returns null when a store_id is specified

[aaguiarz]

When the store-id is not specified, the ouput of fga store import is:

$ fga store import --file store.fga.yaml
{
  "store": {
    "created_at":"2024-05-27T13:37:23.682712Z",
    "id":"01HYX4A87121BGPPFB58J5853Q",
    "name":"store",
    "updated_at":"2024-05-27T13:37:23.682712Z"
  }
}

However, if we specify the ID of an existing store, that does not have a model/tuples, we get null:

$ fga store create --name "test"
{
  "store": {
    "created_at":"2024-05-27T13:38:19.675256Z",
    "id":"01HYX4BYWTVQEWRP6TGVBAJ9TH",
    "name":"test",
    "updated_at":"2024-05-27T13:38:19.675256Z"
  }
}
$ fga store import --store-id 01HYX4BYWTVQEWRP6TGVBAJ9TH --file store.fga.yaml
null

There are two issues:

• When the store is not specified, it needs to return a store + model id, the same way fga store create --file model.fga does, eg:

$ fga store create --model model.fga
{
  "store": {
    "created_at":"2024-05-27T13:40:28.396087Z",
    "id":"01HYX4FWK9P2VFRQ0YABYNQ447",
    "name":"model",
    "updated_at":"2024-05-27T13:40:28.396087Z"
  },
  "model": {
    "authorization_model_id":"01HYX4FWKT84FE3R8C4EJGG7WM"
  }
}

• When the store is specified, it needs to return the data from the current store + the new model:

  $ fga store import --store-id 01HYX4BYWTVQEWRP6TGVBAJ9TH --file store.fga.yaml
  {
  "store": {
  "created_at":"2024-05-27T13:40:28.396087Z",
  "id":"01HYX4BYWTVQEWRP6TGVBAJ9TH",
  "name":"test",
  "updated_at":"2024-05-27T13:40:28.396087Z"
  },
  "model": {
  "authorization_model_id":"01HYX4FWKT84FE3R8C4EJGG7WM"
  }
  }