In this patch we add to docs/new-apis.md (Alternator-specific API)
a description of the service discovery HTTP requests - `/` and
`/localnodes` that was previously not documented except in a design
document that is unfortunately no longer available publically.
The description also includes the recently added `dc` and `rack`
parameters for the `/localnodes` request.
Fixes#20989
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
210d53070e