UPD camt parser: filter empty text nodes and enhance transaction details

[ecino]

This pull request makes several improvements to the CAMT account statement parser, enhancing its robustness and accuracy when extracting transaction details from XML files. The changes focus on handling edge cases in XML parsing, improving reference extraction, and ensuring transaction details are parsed correctly.

Reference and Value Extraction Improvements:

• The list of XPath expressions for extracting transaction references now includes an additional path ("./ns:AcctSvcrRef"), improving coverage for different CAMT file structures.

Transaction Details Handling:

• If no transaction detail nodes are found, the parser now attempts to extract the payment reference from the AddtlNtryInf field, ensuring more complete data extraction.
• When iterating over transaction detail nodes, the parser now:
  • Copies the narration field to each transaction detail.
  • Sets the transaction amount based on the detail amount, if present, or falls back to the main amount if only one detail exists.
  • These changes improve accuracy when splitting or aggregating transaction details.

[davidwul]

the AcctSvcrRef is key to match details debit or credit from a camt054,