Configuring compression of HTTP responses

Exact topics to be determined. Creating this issue as a placeholder so we don't lose it.

https://www.openliberty.io/blog/2020/04/22/http-response-compression.html

Plus:
=== Configuration pitfalls

If the HTTP transport encounters a configuration that is considered invalid, a warning message with an appropriate message is logged. If this happens, the link:https://www.openliberty.io/docs/ref/config/#compression.html[default value for the attribute] that was misconfigured is used.

The following message keys are associated to misconfigurations of the <compression> element's attributes: CWWKT0029W, CWWKT0030W, CWWKT0031W, CWWKT0032W, and CWWKT0033W. For more details of these messages, see the link:https://www.ibm.com/support/knowledgecenter/SSEQTP_liberty/com.ibm.websphere.messages.liberty.doc/com.ibm.ws.http.channel.internal.resources.httpchannelmessages.html[Liberty messages]. <-- This relates to us moving the Messages across to OL docs.

Start with the linked Open Liberty blog post and the compression configuration reference. The issue is a placeholder, so first determine the exact documentation topics and how the CWWKT0029W–CWWKT0033W message information should move into Open Liberty docs. Done means the scope is resolved and the relevant compression configuration pitfalls and messages are documented.