multiFieldOr method
Multi-field OR search (same value across multiple fields)
Example: .multiFieldOr('name', 'email', 'john', operator: 'contains')
Results in: name__or__email_contains=john
Implementation
QueryBuilder multiFieldOr(
List<String> fields,
dynamic value, {
String? operator,
}) {
if (fields.isEmpty) return this;
final fieldKey = fields.join('__or__');
final key = operator != null ? '${fieldKey}__$operator' : fieldKey;
_filters[key] = value;
return this;
}