Pull information from the web service for the target VAT ID :afm_called_for, by the source VAT ID :afm_called_by, with authentication parameters :username and :password.

To create the authentication credentials:

1. Sign up to the "wspublicreg" service using your TAXISnet credentials.
2. Create "special access codes" through the "Διαχείριση Ειδικών Κωδικών" application on TAXISnet.

Regarding the target and source VAT IDs, you will typically pass a valid 9-digit VAT ID, with or without the "EL" prefix. The "EL" prefix will get stripped. Older VAT IDs only have 8 digits, and will get leading-zero-padded to 9 digits.

Note: the function minimizes and checks the source and target VAT IDs, and only sends the request to the API if both minimized VAT IDs are valid.

Same as VatchexGreece.fetch/1, but the resulting tuple is unwrapped. Returns nil if there were errors, otherwise it returns the resulting data.

Pull information from the web service for the target VAT ID afm_called_for defined in the Results struct that has first been created with new/4.

Note: the function minimizes and checks the source and target VAT IDs, and only sends the request to the API if both minimized VAT IDs are valid.

Define a new struct that will be manipulated from containing only the minimal information required to query the SOAP API, to containing the complete request, the SOAP API response, and the parsed information thereof into the corresponding structs.