Handling lower case headers in Rack 2.x

[ioquatix]

rack/lib/rack/etag.rb

Line 37 in 03dd490

unless headers[CACHE_CONTROL]

Some Rack 2.x middleware does not correctly handle lower case headers.

This might cause more pain going forwards as more systems normalise to lower case.

We should probably correctly handle lower case headers. @jeremyevans WDYT?

(For more background see rails/sprockets#746).

[jeremyevans]

I'm OK with additional middleware using headers = Utils::HeaderHash[headers] in Rack 2.x.

[ioquatix]

Okay, I've added this and @tenderlove released 2.2.4 which included this.