EntityTagVersion(etag: String)
EntityTagVersion(etag: String, weak: Boolean)
This version checks etag value and pass it through conditions supplied by the remote client. Depending on conditions it produces return value of enum type VersionCheckResult
It never handles If-None-Match: * as it is related to non-etag logic (for example, Last modified checks). See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.26 for more details
Return
VersionCheckResult.OK if all headers pass or there was no related headers,
VersionCheckResult.NOT_MODIFIED for successful If-None-Match,
VersionCheckResult.PRECONDITION_FAILED for failed If-Match