Add caching header fields as parameters

[Robbilie]

Feature request

just like for X-User-Agent (header) and token (query) i'd like to request if-none-match and possibly if-modified-since to be added.

Route

all

Use case

use swagger-client to pass etags / timestamps (js client ie doesnt allow to set headers manually so this is the only way)

[aquarhead]

Could be integrated with ETag support? @a-tal

[a-tal]

yeah. I'd be ok with an etag qsarg to function as if-none-match