NGF 2.0 banner link for older releases

[sjberman]

Overview

As a v1.6 NGF user,
I want to be able to access my docs after NGF releases 2.0,
So I can still see the proper configurations and architecture for my installed version.

Description

The NGF 2.0 release is changing things up quite a bit, and users take time to upgrade, so users on the previous version will still need access to their docs. We need to make it obvious to them that the current rendered docs are for version 2.0, and that they can access the 1.6 documentation elsewhere.

The current raw 1.6 documentation lives here.

Acceptance criteria

• Using a banner or something obvious, inform NGF users that the current docs are for 2.0, and they can access the 1.6 docs elsewhere.
• Merge into the ngf-release-2.0 branch.

Relevant issue: nginx/nginx-gateway-fabric#3242

[danielledeleo]

This will also require design work in Mainframe.

[ADubhlaoich]

@sjberman there's a few options for handling this: we could link them to the raw documentation, or we could actually have a minimal set of instructions on how to clone and check out an "old" version of the documentation site, since everything is managed with git.

Beyond the banner link, an include or shortcode could be made with the information.

The engineering side for either is relatively easy: what might require some thought is a deprecation timeline.

It wouldn't make much sense to leave the banner up in perpetuity, so there's a few criteria that could be chosen for its removal - such as length of time (X months to to Y years after 2.0 release) or versions (After Z amount of minor or major releases).

[sjberman]

@ADubhlaoich I would say 3 minor releases is a good timeline. That's typically what we've done in terms of deprecating APIs and such.

I'm okay with building instructions if it's simple enough for a user to do. If it involves downloading tools and source code, etc. it might be too much.