Recommend use of the Vary header in version 2 of the Users Guide

[ghobona]

During the 2022-11 Web Mapping Code Sprint, there was feedback that to prevent the server from caching responses in some cases, it might be necessary to use the Vary header.

[ghobona]

@jerstlouis Please elaborate.

[jerstlouis]

For resource end-points that may return a different representation for the content encoded differently based on request headers, any header value should be included as part of a Vary: response header.
e.g., Vary: Accept, Accept-Encoding, Prefer

This will avoid issues with proxying / caching.