[MAR-42] Dynamic registration only allows for 1 device to be registered at a time on Epic

[cfu288]

When authenticating to an Epic source using the dynamic registration flow, only one device (aka one private key) can be registered at a time. Since we don't currently share private keys across devices, only the last signed in device can refresh data. Any devices (privkeys) that were previously registered to the same epic source become unregistered

_{From SyncLinear.com | MAR-42}

[cfu288]

May need to implement an API endpoint and user login on the backend to enable storing and sharing public keys across multiple devices for a user. That way when a new epic dynamic registration happens, we can send over all public keys at once during dynamic registration on a new device.