fix Max-Age handling with tests

lib/HTTP/CookieJar.pm

@@ -67,7 +67,12 @@ sub add {
     # set timestamps and normalize expires
     my $now = $parse->{creation_time} = $parse->{last_access_time} = time;
     if ( exists $parse->{'max-age'} ) {
-        $parse->{expires} = $now + delete $parse->{'max-age'};
+        # "If delta-seconds is less than or equal to zero (0), let expiry-time
+        # be the earliest representable date and time."
+        $parse->{expires} = $parse->{'max-age'} <= 0
+            ? 0
+            : $now + $parse->{'max-age'};
+        delete $parse->{'max-age'};
     }
     # update creation time from old cookie, if exists
     if ( my $old = $self->{store}{$domain}{$path}{$name} ) {

t/add.t

@@ -207,6 +207,33 @@ my @cases = (
             },
         },
     },
+    # check that Max-Age supercedes Expires and that Max-Age <= 0 forces
+    # expiration
+    {
+        label   => "max-age supercedes expires",
+        request => "http://example.com/",
+        cookies => [
+            "lang=en-us; Max-Age=100; Expires=Thu, 1 Jan 1970 00:00:00 GMT",
+            "SID=31d4d96e407aad42; Expires=Thu, 3 Jan 4841 00:00:00 GMT",
+            "SID=0000000000000000; Max-Age=0",
+        ],
+        store   => {
+            'example.com' => {
+                '/' => {
+                    lang => {
+                        name             => "lang",
+                        value            => "en-us",
+                        expires          => ignore(),
+                        creation_time    => ignore(),
+                        last_access_time => ignore(),
+                        domain           => "example.com",
+                        hostonly         => 1,
+                        path             => "/",
+                    },
+                },
+            },
+        },
+    },
 );
 
 for my $c (@cases) {