Write test for StripeConnectAccount.update_from_stripe/1

# Problem

Test should ensure the function returns an {:ok, %StripeConnectAccount{}} with valid data. It should also ensure that the record was actually updated with data from stripe testing.

An additional test should ensure that, if there is no local record with the specified `id_from_stripe`, the response is `{:error, :not_found}`

Lastly, a test should ensure that, if the attributes provided contain invalid data, an `{:error, changeset}` is returned.

### Something we cannot test right now, since we do not have the infrastructure
* If the stripe API raises an error, it returns `{:error, %StripeAPIErrorResponse{}}`