Remove GetResult and GetInfo APIs (#25)

This spec is being repurposed as a system integration spec, instead of
an application level protocol.
As part of this change, we are stripping the spec down to the bare
minimum that is required for its new purpose.

---------

Co-authored-by: pdoerner <[email protected]>

Author: bergundy

SPEC.md

@@ -2,13 +2,14 @@
 
 ## Overview
 
-The Nexus protocol, as specified below, is a synchronous RPC protocol. Arbitrary duration operations are modelled on top
-of a set of pre-defined synchronous RPCs.
+The Nexus protocol, as specified below, is a synchronous RPC protocol for system-to-system integration. Arbitrary
+duration operations are modelled on top of a set of pre-defined synchronous RPCs.
 
 A Nexus **caller** calls a **handler**. The handler may respond inline (synchronous response) or return a token
-referencing the ongoing operation (asynchronous response). The caller can cancel an asynchronous operation, check for
-its outcome, or fetch its current state. The caller can also specify a callback URL, which the handler uses to deliver
-the result of an asynchronous operation when it is ready.
+referencing the ongoing operation (asynchronous response), which the the caller use to cancel the operation. In lieu of
+a higher level service contract, the caller cannot determine whether an operation is going to resolve synchronously or
+asynchronously, and should specify a callback URL, which the handler uses to deliver the result of an asynchronous
+operation when it is ready.
 
 ## Operation Addressability
 
@@ -185,109 +186,6 @@ The operation token received as a response to the Start Operation method must be
 
   **Body**: A JSON serialized [`Failure`](#failure) object.
 
-### Fetch Operation Result
-
-Retrieve operation result.
-
-**Path**: `/{service}/{operation}/result`
-
-**Method**: `GET`
-
-#### Request Headers
-
-The operation token received as a response to the Start Operation method must be delivered either via the
-`Nexus-Operation-Token` header field or the `token` query param.
-
-#### Query Parameters
-
-- `token`: The operation token received as a response to the Start Operation method. Must be delivered either via the
-  `token` query param or the `Nexus-Operation-Token` header field.
-
-- `wait`: Optional. Duration indicating the waiting period for a result, defaulting to no wait. If by the end of the
-  wait period the operation is still running, the request should resolve with a `412` status code (see below).
-
-  Format of this parameter is number + unit, where unit can be `ms` for milliseconds, `s` for seconds, and `m` for
-  minutes. Examples:
-
-  - `100ms`
-  - `1m`
-  - `5s`
-
-#### Response Codes
-
-- `200 OK`: Operation completed successfully.
-
-  **Headers**:
-
-  - `Nexus-Operation-State: succeeded`
-
-  **Body**: Arbitrary data conveying the operation's result. Headers should specify content type and encoding.
-
-- `408 Request Timeout`: The handler gave up waiting for operation completion. The request may be retried by the caller.
-
-  **Body**: Empty.
-
-- `412 Precondition Failed`: Operation still running.
-
-  When waiting for completion, the caller may re-issue this request to start a new long poll.
-
-  **Body**: Empty.
-
-- `424 Failed Dependency`: Operation completed as `failed` or `canceled`.
-
-  **Headers**:
-
-  - `Content-Type: application/json`
-  - `Nexus-Operation-State: failed | canceled`
-
-  **Body**: A JSON-serialized [`Failure`](#failure) object.
-
-- `404 Not Found`: Operation token not recognized or references deleted.
-
-  **Headers**:
-
-  - `Content-Type: application/json`
-
-  **Body**: A JSON-serialized [`Failure`](#failure) object.
-
-### Fetch Operation Info
-
-Retrieve operation details.
-
-**Path**: `/{service}/{operation}`
-
-**Method**: `GET`
-
-#### Request Headers
-
-The operation token received as a response to the Start Operation method must be delivered either via the
-`Nexus-Operation-Token` header field or the `token` query param.
-
-#### Query Parameters
-
-- `token`: The operation token received as a response to the Start Operation method. Must be delivered either via the
-  `token` query param or the `Nexus-Operation-Token` header field.
-
-#### Response Codes
-
-- `200 OK`: Successfully retrieved info.
-
-  **Headers**:
-
-  - `Content-Type: application/json`
-
-  **Body**:
-
-  A JSON-serialized [`OperationInfo`](#operationinfo) object.
-
-- `404 Not Found`: Operation token not recognized or references deleted.
-
-  **Headers**:
-
-  - `Content-Type: application/json`
-
-  **Body**: A JSON-serialized [`Failure`](#failure) object.
-
 ## Predefined Handler Errors
 
 For compatiblity of this HTTP spec with future transports, when a handler fails a request, it **should** use one of the