[Refactor] `fetchResponse` in function return signatures should be optional

[nkshah2]

Each recipe function that makes a network call has a fetchResponse in its return signature which contains the original response object.

The problem this causes is that if the function is overridden and the logic is changed to not make a network call, you are forced to pass new Response() when returning. This is a bad interface to have any making the fetchResponse optional will solve this.