Add password authentication to demo election

demo/data/6d122f00-2650-4de8-87de-30037a21f943/metadata.json

-{"owner":{"domain":"demo","name":"admin"},"readers":"Any","voters":"Any","auth_config":[{"auth_system":"dummy","auth_instance":"demo","auth_config":[]}]}
+{"owner":{"domain":"demo","name":"admin"},"readers":"Any","voters":"Any","auth_config":[{"auth_system":"dummy","auth_instance":"demo","auth_config":[]},{"auth_system":"password","auth_instance":"password","auth_config":[["db","foo.bar"]]}]}