Set Expires headers for Hydra's binary cache

This allows caching by reverse proxies.

src/lib/Hydra/Helper/CatalystUtils.pm

@@ -28,6 +28,7 @@ our @EXPORT = qw(
     showJobName
     showStatus
     getResponsibleAuthors
+    setCacheHeaders
 );
 
 
@@ -305,4 +306,12 @@ sub getResponsibleAuthors {
 }
 
 
+# Set HTTP headers for the Nix binary cache.
+sub setCacheHeaders {
+    my ($c, $expiration) = @_;
+    $c->response->headers->expires(time + $expiration);
+    delete $c->response->cookies->{hydra_session};
+}
+
+
 1;