allowing more extensibility to customize the mqtt events logged in the database

[ionutab]

Added this to allow the option for users to customize the events logged in the database.
This would be done by extending the MqttClient class and overriding the _generate_event_name method.
For example when sending messages on a large variety of topics this generates a very fuzzy and hard-to-read set of charts in Grafana.
A more generic, simple view may be required.
Altering the queries in the Grafana dashboards to simplify the charts can be error-prone, performance downgrading, and will create maintenance overhead.
This solution allows users to alter the logged entry in the database for a more use-case-centric grouping.
I can provide more details of required - like a very simple dataset.
Thank you

[cyberw]

Lgtm, but could you add an example of how to use it? In mqtt_ex.py or a separate one.

[ionutab]

sure thing,
after I fix the linting issue

[ionutab]

@cyberw thanks!