Create a cloud-iox ref contract containing a subset of cloud endpoints

Nobody has claimed this yet.

In order to build Cloud IOx HTTP API documentation, we need a contract(s) defining the relevant endpoints for IOx.

For docs' purposes alone, we can achieve this a few different ways:

- Option 1: a complete ./contracts/ref/cloud-iox.yml contract maintained in this repo.
- Option 2: a list of the relevant tags (if we don't need to exclude specific operations) maintained either in this repo or in docs-v2.
- Option 3: a list of the relevant paths and operations (if Option 2 isn't "surgical" enough).

Questions:
- Is Option 1 the "correct" way?
- If so, is anyone working on that?

I've shared a [doc](https://docs.google.com/document/d/1d9YBEAWAbWwHCMw_3a2Ib5Tu7MeQTV_8Z2_Ly9lELh4/edit?usp=sharing) to gather consensus on which current Cloud v2 endpoints are (or will be) relevant for IOx.

Start with the shared Cloud v2 endpoint consensus document and compare the proposed approaches with ./contracts/ref/ and docs-v2. Done means the relevant IOx endpoints are agreed and represented by the selected contract, tag list, or path/operation list.

Written by the indexing model from the issue text.