Simplify mocking of iterator and waiter objects

[mgyucht]

Changes

It is currently challenging to mock APIs that return iterator structs like *listing.PaginatedIterator or *listing.DedupedIterator. To simplify mocking of iterator responses, we can change the return type for these methods to return the listing.Iterator interface. Then, users who need to write tests can use listing.SliceIterator to mock the response, for example:

w.GetMockWarehousesAPI().EXPECT().List(mock.Anything, mock.Anything).Return(&listing.SliceIterator[sql.EndpointInfo]{
	{
		Id:   "1",
		Name: "foo",
	},
	{
		Id:   "2",
		Name: "bar",
	},
})

Similarly, methods returning Wait* objects are difficult to mock. The Get() method calls the internal poll field, but that cannot be set by users who want to mock the response. Exposing this method allows users to define mock responses, for example:

w.GetMockWarehousesAPI().EXPECT().Create(mock.Anything, createRequest).Return(&sql.WaitGetWarehouseRunning[sql.CreateWarehouseResponse]{
	Poll: poll.Simple(getResponse),
}, nil)

Callers can then call w.Warehouses.Create(...).Get().

Lastly, waiters for which the initial method doesn't have a response have a type parameter of any which cannot be mocked easily. Instead, I changed this to struct{} to indicate that the response is empty.

Tests

• Unit tests for new helper functionality.