registerDriver method
Registers a session driver with the given name.
Implementation
@override
void registerDriver(String name, SessionDriver driver) {
if (name.isEmpty) {
throw ArgumentError('Driver name cannot be empty');
}
if (_drivers.containsKey(name)) {
throw StateError('Driver "$name" is already registered');
}
_drivers[name] = driver;
// Set as default if it's the first driver
_defaultDriverName ??= name;
}