Add support to error response on specific endpoints

[javaherisaber]

Problem statement

I want to return error response for a specific endpoint eg. 500 error

Possible solution

Just like apiIncludeIntoMock array, we can pass another object to define which endpoints to show error

eg. a list of this pair
"[POST] customer/cart/{id}/update2" to 500

Alternative solutions

We can also provide a way to pass error response body for each error code into MockFit constructor
so that we can use it to return error body