Dates in return types are deserialized as strings

[etiago]

Environment

Node version: 8.10
Npm version: 5.8.0
OS and version: MacOS 10.13.3
typed-rest-client version: stable

Issue Description

When using a type for the response which has Date as type for a field, that field ends up being a string, thus violating the type.

Expected behaviour

If I have a field which is a Date, I expect the deserialization to fail whenever the returned type isn't a date, or if the type does represent a parseable Date, that the field gets correctly transformed into a Date.

Actual behaviour

Instead of a Date, we get string. This means that any code that I write expecting there to be a Date, becomes type-unsafe as all the Date methods are not available in string objects.

Steps to reproduce

1. Create type class with Date field.
2. Make request to endpoint which returns a string-encoded standard JSON Date for that field.
3. Verify that none of the Date methods are available in the deserialized object.

As I understand, this may be tricky to solve as JSON.parse will see a string and leave it as a string. However, we could possibly introspect the type of the response and handle the Date manually.

[bryanmacfarlane]

@damccorm - good issue. think through compat on potential fixes.