1.12.0

• Break: HandlerInterface::isHandling now receives a partial record containing only a level key. This was always the intent and does not break any Monolog handler but is strictly speaking a BC break and you should check if you relied on any other field in your own handlers.
• Added PsrHandler to forward records to another PSR-3 logger
• Added SamplingHandler to wrap around a handler and include only every Nth record
• Added MongoDBFormatter to support better storage with MongoDBHandler (it must be enabled manually for now)
• Added exception codes in the output of most formatters
• Added LineFormatter::includeStacktraces to enable exception stack traces in logs (uses more than one line)
• Added $useShortAttachment to SlackHandler to minify attachment size and $includeExtra to append extra data
• Added $host to HipChatHandler for users of private instances
• Added $transactionName to NewRelicHandler and support for a transaction_name context value
• Fixed MandrillHandler to avoid outputing API call responses
• Fixed some non-standard behaviors in SyslogUdpHandler