Treat "Accept-Encoding: *" as not accepting any encoding

[rtibbles]

• Adds support for "*" Accept-Encoding value
• Makes Accept-Encoding default to this value when missing as per spec
• Adds tests for both values

Fixes #303

[adamchainz]

I feel a bit uneasy about sending compressed data to clients that don't necessarily support it. It would probably be better to return the non-compressed version.

For reference, I checked what nginx does. I found here in its gzip plugin that it seems to bail out if no Accept-Encoding header is provided, or if gzip isn't explicitly mentioned: https://github.com/nginx/nginx/blob/1f01183b9e6658749934313fd72f7f16c1918b54/src/http/ngx_http_core_module.c#L2037-L2040

Copying this approach seems more sensible than returning the smallest compressed response.

Would you be willing to update the PR? Afaict it requires a bit more rework since alternatives is only sorted by size, but you explicitly want the not-compressed version.

[rtibbles]

Can update - I don't think it will be difficult, can just revert the change that updates the default to "*" when the value is missing and put it back to "".

[rtibbles]

Updated the PR.