Same User Logged in From Two Locations

[rmacgill]

Right now, the same user can log in from two devices. This isn't inherently an issue, but it causes some weird state interactions when creating and deleting ride requests since the device that didn't initiate an update won't always have an update pushed to it from Firestore.

[hmp31]

In checking this out this requires a decent amount of work to fix. Firebase does not provide any easy way of doing this. We will likely have to implement a lock (boolean) table on firebase keyed by UID to enforce being signed in with only one account. I think the only way we can prevent the user from accidentally locking their account permanently (such as if their app is forced shut unexpectantly) is to somehow log out the previous logged in device.