Azure API reference for Reserved Instances is missing 'write' operations

This is issue transferred from https://github.com/MicrosoftDocs/feedback/issues/576.

**Link to article:**
https://docs.microsoft.com/en-us/rest/api/reserved-vm-instances/

**Link to swagger:**
https://github.com/Azure/azure-rest-api-specs/blob/master/specification/reservations/resource-manager/Microsoft.Capacity/stable/2017-11-01/reservations.json

**Problem:**
Look at the various sub-pages for resources/operations relating to Reserved Instances.
All I can see are 'Read' operations. Where is the API reference for the 'Write' operations? How do I use the REST API to create a Reserved Instance?

According to the sample output at https://docs.microsoft.com/en-us/rest/api/reserved-vm-instances/operation/list there should be write operations on 'reservations' and 'reservationOrders'.

Start with specification/reservations/resource-manager/Microsoft.Capacity/stable/2017-11-01/reservations.json and compare its operations with the Reserved Instances article and the operation/list sample. Determine whether write operations for reservations and reservationOrders are present in the specification but absent from the generated reference. Done means the API reference documents the requested write operations and explains how to create a Reserved Instance.

Written by the indexing model from the issue text.