Function to_authorize 

pub fn to_authorize(
    request_xml: &str,
    response_xml: &str,
) -> Result<String, FiscalError>

Detect the document type from raw XML and dispatch to the correct protocol-attachment function.

This mirrors the PHP Complements::toAuthorize() method, which uses Standardize::whichIs() internally. The detection logic checks for the same root tags in the same priority order as the PHP implementation:

Detected tag	Dispatches to
NFe	attach_protocol
envEvento	attach_event_protocol
inutNFe	attach_inutilizacao

Errors

Returns FiscalError::XmlParsing if:

• Either input is empty
• The request XML does not match any of the known document types
• The delegated function returns an error