Create 2024-08-30-position-privacy.md

[jp-bennett]

Position and MQTT Privacy fixes

https://github.com/meshtastic/rfcs/blob/position-mqtt-privacy/rfcs/2024-08-30-position-privacy.md

Summary

Add home zones, where the user can pick a position on the map, and a precision value, to send limited precision packets while in the zone. Additionally, add a DoNotMQTT bit to the Data protobuff, to indicate that other nodes should not forward packets to an MQTT server, default true.

[b8b8]

I think this is a perfect solution to our problem at hand.

The home-zones are firmware based so cannot be bypassed (by 3rd parties) and their configurability will allow users to set zones even the size of cities. Once outside one's neighborhood the identifiability of an individual is lessened. Functionality will be restored to the MQTT maps for all those that want precise tracking as they can simply manually disable the home-zone or place it at Null Island.

The MQTT do-not-track flag shows user's intent that will hopefully keep the MQTT maps honest, but if they choose not to, the home-zone is a robust backup. At the very least, users can be confident the official Meshtastic MQTT server will honor the flag.