fn decode_account(qr: &str) -> Result<Qr>
scheme: DCACCOUNT:example.org or DCACCOUNT:https://example.org/new or DCACCOUNT:https://example.org/new_email?t=1w_7wDjgjelxeX884x96v3
DCACCOUNT:example.org
DCACCOUNT:https://example.org/new
DCACCOUNT:https://example.org/new_email?t=1w_7wDjgjelxeX884x96v3