Support header only consumers

[ripienaar]

Overview

Consumers have an option to enable delivering just headers. When delivering just headers an additional header Nats-Msg-Size is added indicating the size of the omitted body.

Server PR https://github.com/nats-io/nats-server/pull/2596 Schemas in https://github.com/nats-io/jsm.go/pull/333

These features are required for ADR-8

Clients and Tools

• [x] Schemas @ripienaar
• [x] CLI @ripienaar (https://github.com/nats-io/natscli/pull/259)
• [x] Terraform @ripienaar
• [x] Github Actions @ripienaar
• [x] Go @wallyqs (https://github.com/nats-io/nats.go/pull/832)
• [x] Java @scottf
• [x] JavaScript @aricart
• [x] .Net @ColinSullivan1 @scottf
• [x] C @kozlovic
• [x] Python @wallyqs
• [x] Rust @Jarema

Other Tasks

• [x] docs.nats.io updated
• [x] Update client features spreadsheet

Client authors please update with your progress. If you open issues in your own repositories as a result of this request, please link them to this one by pasting the issue URL in a comment or main issue description.

[bruth]

Python implemented in https://github.com/nats-io/nats.py/pull/216 Docs PR here; https://github.com/nats-io/nats.docs/pull/482