mod_http_file_share: Include expiry time of the upload itself in token

Lets an external upload service know this so it can do expiry itself.
Could possibly have been calculated based on the token expiry or
issuance time, explicit > implicit.

plugins/mod_http_file_share.lua

@@ -142,6 +142,7 @@ local now = os.time();
 
 		-- slot properties
 		slot = slot;
+		expires = expiry >= 0 and (now+expiry) or nil;
 		-- file properties
 		filename = filename;
 		filesize = filesize;