If set up, this hub will be used to subscribe to feeds that don't specify a hub of their own.
Assumes that the fallback hub will, in fact, handle polling and updates for any feed we throw at it!
Authentication may be specified for the fallback hub.
Example:
$config['feedsub']['fallback_hub'] = 'https://superfeedr.com/hubbub';
$config['feedsub']['hub_user'] = 'abcd';
$config['feedsub']['hub_pass'] = 'ckcmdkmckdmkcdk';
Also:
* Fix for WordPress-RSS-via-Superfeedr-Atom; if we have <author> info but no ID from a native ActivityStreams actor, don't freak out in the low-level processing code that checks for identity matches.
* enhanced messages for low-level FeedSub exceptions if they make it to outside display
The code pattern 'new XXXException($e)' to chain exceptions doesn't actually work as intended, as exceptions are actually expecting a string message here.
This caused an implicit string conversion from HTTP_Request2_Exception, which is a PEAR_Exception, which defines an absurdly detailed __toString() method including a giant HTML table with a backtrace if you happen to be on a web request.
Simply passing $e->getMessage() instead clears this up, as we'll get the nice short message like 'Couldn't connect to tcp://blahblah:80'
Parsing hcards for the data we need wasn't hard enough to justify using
hkit. It was dependent on a number of external systems (something to
run tidy), and only could handle XHTML.
We now parse HTML with the PHP dom libraries used elsewhere, and
scrape out our own hcards. Seems to work nicer and faster and most of
all works with Google Buzz profile URLs.
* Subscription::start was sometimes passing users instead of profiles to hooks, which broke OStatus subscription notifications; now normalizing to profiles for processing.
* H-card parsing would trigger a lot of PHP warnings and notices in hKit. Now suppressing warnings and notices for the duration of the call to keep them out of output when display_errors is on.
* H-card parsing would trigger a PHP fatal error if the source page was not well-formed XML and Tidy was not present on the system. Switched normalization to use the PHP DOM module which is always present, as we have no need for Tidy's extra features here.
* Trying to fetch avatars from Google profiles failed and triggered a PHP warning due to the relative URL not being resolved during h-card parsing. Now passing profile page URL into hKit by sneaking a <base> tag in while we normalize the HTML source.
* Profile pages without a "Link" header could trigger PHP notices due to a bad NULL -> array(NULL) conversion in LinkHeader::getLink(). Now checking that there was a return value before converting single return value into array.
