allow to set user data in the init method

[vladak]

This change allows to set the opaque user data in the init method. Works like this:

"""
MQTT utility functions
"""
import ssl

import adafruit_logging as logging
import adafruit_minimqtt.adafruit_minimqtt as MQTT

# pylint: disable=unused-argument, redefined-outer-name, invalid-name
def connect(mqtt_client, userdata, flags, rc):
    """
    This function will be called when the mqtt_client is connected
    successfully to the broker.
    """
    logger = userdata

    logger.info("Connected to MQTT Broker!")
    logger.debug(f"Flags: {flags}\n RC: {rc}")

# pylint: disable=unused-argument, invalid-name
def disconnect(mqtt_client, userdata, rc):
    """
    This method is called when the mqtt_client disconnects from the broker.
    """
    logger = userdata

    logger.info("Disconnected from MQTT Broker!")

def publish(mqtt_client, userdata, topic, pid):
    """
    This method is called when the mqtt_client publishes data to a feed.
    """
    logger = userdata

    logger.info(f"Published to {topic} with PID {pid}")

def mqtt_client_setup(pool, broker, port):
    """
    Set up a MiniMQTT Client
    """

    logger = logging.getLogger("mqtt")
    logger.setLevel(logging.DEBUG)

    mqtt_client = MQTT.MQTT(
        broker=broker,
        port=port,
        socket_pool=pool,
        ssl_context=ssl.create_default_context(),
        user_data=logger,
    )

    mqtt_client.on_connect = connect
    mqtt_client.on_disconnect = disconnect
    mqtt_client.on_publish = publish

    return mqtt_client

def main():
    import socket
    mqtt_client = mqtt_client_setup(broker="localhost", port=1883, pool=socket)
    mqtt_client.connect()
    mqtt_client.publish("foo/bar", "msg")

if __name__ == "__main__":
    main()

Tested with CPython against custom MQTT broker implementation, produces the following output:

601394.401: INFO - Connected to MQTT Broker!
601394.401: DEBUG - Flags: 0
 RC: 0
601394.401: INFO - Published to foo/bar with PID 0