If-None-Match header takes precedence over If-Modified-Since and allows caching http clients to refresh the content only if content etag changes. Right now, only aiohttp server supports only If-Modified-Since header but not If-None-Match

💡 Describe the solution you'd like
If GET/HEAD request contains If-None-Match, the server should check for the resource etag and, it the etag matches the value in If-None-Match header, return Not Modified 304. More details are in RFC2616

❓ Describe alternatives you've considered
None