Add template interceptor type definition

[optical]

Adds definition for the template interceptor.

See https://github.com/cujojs/rest/blob/master/docs/interceptors.md#module-rest/interceptor/template

[dt-bot]

rest/rest.d.ts

to author (@Nemo157). Could you review this PR?
👍 or 👎?

Checklist

• pass the Travis CI test?

[Nemo157]

Should the type of params be { [key: string]: any }?

[optical]

Yeah I wasn't certain about that - I think its more correct though, so will change.

Also, with the tests the current ones all have the config type set to any when calling wrap. Should these explicitly use their corresponding config type where appropriate?

    .wrap<defaultRequest.Config>(defaultRequest)
    .wrap<hateoas.Config>(hateoas)
    .wrap<location.Config>(location)

And so forth, or is there a reason not to do this?

It'd be nice if these types could always be correctly inferred, but I can't seem to get to work.

[optical]

Actually it does seem to infer the types properly most of the time.

With the current incorrect definition it'll infer the config type to be template.Config and will error out because of the extra property.
rest.wrap(template, { params: { extra: 'bang!' } });

However surprisingly this will compile just fine?
rest.wrap<template.Config>(template, { params: { extra: 'bang!' } });

So with the tests I could change them to use inference wherever appropriate, and fill out corresponding stub config too.

Does this sound reasonable?

[Nemo157]

Weird that it works with the explicit type... Changing to use inference everywhere would be good, they may have improved the inference since I first added the config checking.

[Nemo157]

Ah, looks like it broke on TS1.6 for some reason (486828c and #5590). If changing back to inferred types works then that would be good. I do remember having some issues with the inference not always working, but can't remember exactly what they were.

[optical]

Inference doesn't work here

[Nemo157]

Ahh, it's failing to derive the correct type for knownConfig as it doesn't have an init method in the config it passes to interceptor. There's probably some way to change the definition of rest/interceptor to allow it to correctly derive it.

[Nemo157]

👍