This implementation is similar to AMQP notifications:
* Notifications are published on a single topic as a JSON feed
* Topic is configurable, as is the QoS. Uses the paho.mqtt.golang
library for the mqtt connection, and supports connections over tcp
and websockets, with optional secure tls support.
* Additionally the minio server configuration has been bumped up
so mqtt configuration can be added.
* Configuration migration code is added with tests.
MQTT is an ISO standard M2M/IoT messaging protocol and was
originally designed for applications for limited bandwidth
networks. Today it's use is growing in the IoT space.
* Add configuration parameter "format" for db targets and perform
configuration migration.
* Add PostgreSQL `access` format: This causes Minio to append all events
to the configured table. Prefix, suffix and event filters continue
to be supported for this mode too.
* Update documentation for PostgreSQL notification target.
* Add MySQL `access` format: It is very similar to the same format for
PostgreSQL.
* Update MySQL notification documentation.
