unique method
Adds a unique index across the provided columns.
Implementation
IndexDefinition unique(
Iterable<String> columns, {
String? name,
Map<String, Map<String, Object?>>? driverOptions,
}) {
return _addIndex(
columns,
IndexType.unique,
nameSuffix: 'unique',
explicitName: name,
driverOptions: driverOptions,
);
}