Return person identifier field specification for a specific validation method. The validation_method parameter should match one of the available methods (e.g., 'ariregister', 'wirtschaftscompass', 'bolagsverket', 'breg').
Field specification for person identification. For simple identifiers: {type: 'string', field: 'civil_number', ...}. For composite identifiers: {type: 'object', fields: {...}}
Return list of supported countries for validation
Return list of supported countries for validation.