Feature: Response delay

[bstien]

Why?

Responses are currently delivered immediately, but one might want to delay a response for n seconds. Immediate delivery is still the default, but this adds support for delaying the response.

What?

• Add MockResponse.Delivery
  • Has cases .instant and .delayed(TimeInterval)
• Add tests

Show me

HTTPMock.shared.addResponses(
    forPath: "/root",
    responses: [
        .empty(delivery: .instant),     // Delivered immediately on request.
        .empty(delivery: .delayed(2.0)) // Response delivery is delayed for 2 seconds.
    ]
)