Implementing TTRSS: Subscribe to a Feed #92

subscribeToFeed (API level 5 - version:1.7.6)

Subscribes to specified feed, returns a status code. See
subscribe_to_feed() in functions.php for details.

Parameters:

feed_url - Feed URL (string)
category_id - Category id to place feed into (defaults to 0, Uncategorized) (int)
login, password - Self explanatory (string)

The return codes are:

	/**
	 * @return array (code => Status code, message => error message if available)
	 *
	 *                 0 - OK, Feed already exists
	 *                 1 - OK, Feed added
	 *                 2 - Invalid URL
	 *                 3 - URL content is HTML, no feeds available
	 *                 4 - URL content is HTML which contains multiple feeds.
	 *                     Here you should call extractfeedurls in rpc-backend
	 *                     to get all possible feeds.
	 *                 5 - Couldn't download the URL content.
	 *                 6 - Content is an invalid XML.
	 */

Additionally, it -does- also return the added subscription ID for codes 0 or 1.

Because TTRSS returns the existing subscription ID upon duplication, we'll need a backend function to discover a feed URL manually (picoFeed does expose the functionality, though not terribly cleanly), probably as a static method of the Feed class.

Example output:

{"seq":0,"status":0,"content":{"status":{"code":1,"feed_id":8}}}

{"seq":0,"status":0,"content":{"status":{"code":5,"message":"6 Could not resolve host: example"}}}