First steps on converting FeedSub into the pub/sub basis for OStatus communications:

* renamed FeedSub plugin to OStatus
* now setting avatar on subscriptions
* general fixes for subscription
* integrated PuSH hub to handle only user timelines on canonical ID url; sends updates directly
* set $config['feedsub']['nohub'] = true to test w/ foreign feeds that don't have hubs (won't actually receive updates though)
* a few bits of code documentation
* HMAC support for verified distributions (safest if sub setup is on HTTPS)

And a couple core changes:
* minimizing HTML output for exceptions in API requests to aid in debugging
* fix for rel=self link in apitimelineuser when id given

This does not not yet include any of the individual subscription management (Salmon notifications for sub/unsub, etc) nor a nice UI for user subscriptions.
Needs some further cleanup to treat posts as status updates instead of link references.

plugins/OStatus/lib/hubverifyqueuehandler.php

@@ -0,0 +1,53 @@
+<?php
+/*
+ * StatusNet - the distributed open-source microblogging tool
+ * Copyright (C) 2010, StatusNet, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * Send a PuSH subscription verification from our internal hub.
+ * @package Hub
+ * @author Brion Vibber <brion@status.net>
+ */
+class HubVerifyQueueHandler extends QueueHandler
+{
+    function transport()
+    {
+        return 'hubverify';
+    }
+
+    function handle($data)
+    {
+        $sub = $data['sub'];
+        $mode = $data['mode'];
+
+        assert($sub instanceof HubSub);
+        assert($mode === 'subscribe' || $mode === 'unsubscribe');
+
+        common_log(LOG_INFO, __METHOD__ . ": $mode $sub->callback $sub->topic");
+        try {
+            $sub->verify($mode);
+        } catch (Exception $e) {
+            common_log(LOG_ERR, "Failed PuSH $mode verify to $sub->callback for $sub->topic: " .
+                                $e->getMessage());
+            // @fixme schedule retry?
+            // @fixme just kill it?
+        }
+
+        return true;
+    }
+}
+