Currently, YANG notification processing is done using a special type of
callbacks registered in backend clients. In this commit, we start using
regular northbound infrastructure instead, because it already has a
convenient way of registering xpath-specific callbacks without the need
for creating additional structures for each necessary notification. We
also now pass a notification data to the callback, instead of a plain
JSON. This allows to use regular YANG library functions for inspecting
notification fields, instead of manually parsing the JSON.
Signed-off-by: Igor Ryzhov <iryzhov@nfware.com>
Current code assumes that notification is always sent in stripped JSON
format and therefore notification xpath starts at the third symbol of
notification data. Assuming JSON is more or less fine, because this
representation is internal to FRR, but the assumption about the xpath is
wrong, because it won't work for not top-level notifications. YANG
allows to define notification as a child for some data node deep into
the tree and in this case notification data contains not only the
notification node itself, but also all its parents.
To fix the issue, parse the notification data and get its xpath from its
schema node.
Signed-off-by: Igor Ryzhov <iryzhov@nfware.com>
