Add MQTT Sink

[SteveRosam]

Added MQTT connector
Added tests
Updated pyproject.toml
Updated tests/requirement.txt

Resolves #658

[daniil-quix]

Suggested change

	mqtt_client_id: str,
	mqtt_server: str,
	mqtt_port: int,
	mqtt_topic_root: str,
	mqtt_username: str = None,
	mqtt_password: str = None,
	mqtt_version: str = "3.1.1",
	tls_enabled: bool = True,
	qos: int = 1,
	client_id: str,
	server: str,
	port: int,
	topic_root: str,
	username: str = None,
	password: str = None,
	version: str = "3.1.1",
	tls_enabled: bool = True,
	qos: int = 1,

[devova]

@SteveRosam I also need this sink and willing to contribute to your PR if you don't mind

[devova]

Some sinks has concept of

value_serializer: Callable[[Any], str] = json.dumps,
key_serializer: Callable[[Any], str] = bytes.decode,

in its constructors. That is very handy, specially when you are dealing with non json data. I don't see a use case for key_serializer, but value_serializer is definitely something nice to have.

[devova]

According to docs, it would be great to have a control over retain and properties arguments.
Ideally the constructor should accept either constant or callbacks

retain: bool | Callable[[Any], bool] = False,
properties: paho.mqtt.properties.Properties | Callable[[Any], paho.mqtt.properties.Properties] | None = None,

[devova]

It would be good to add sync primitive here. Client.publish returns MQTTMessageInfo which has
wait_for_publish()

Suggested change

	self.mqtt_client.publish(
	self.message_infos.add(self.mqtt_client.publish(...))
	def flush(self, topic: str, partition: str):
	for message_info in self.message_infos:
	message_info.wait_for_publish()

see quix-streams sink flush docs