Externally-hosted Compatibility Matrix is down

[yaauie]

In our docs, we link to an externally-hosted compatibility matrix at the following URL:

https://cwiki.apache.org/confluence/display/KAFKA/Compatibility+Matrix

But that URL is emitting 503 Service Unavailable for at least the last hour; while the Apache Software Foundation Wiki is generally pretty reliable, this ticket is to ensure we don't lose track, and come up with a way to ensure availability of the matrix to our users.

[jsvd]

this ticket is to ensure we don't lose track, and come up with a way to ensure availability of the matrix to our users.

We can clone the contents of that wiki page, but the idea with this reference was to exactly lead users to confluence when it's necessary to understand compatibility.