implementation of roles logic

[festivixy]

Right now, there are a few logic errors with the system.

1. A person signing up as a rider (ONLY) should not be able to see any of the driver-specific functions (e.g. my rides)]
2. A person signing up as a driver (ONLY) should not be able to join a ride as a rider.

This also prevents a driver joining a ride as a rider, and then being asked to text "the rider".

Create a logic system for a person who wishes to be part of both roles.

[festivixy]

@zlc1004 check