A literal type for controlling table creation mode.
In TypeScript: type CreateMode = "create" | "overwrite" | "create_if_not_exists";
In Dart, we can use an enum or string constants. Here we'll use an enum.
Decodes any base64-encoded fields in the list of record maps.
If a value is a map with {"encoding": "base64", "data": ...},
it will be replaced with a Uint8List containing the decoded bytes.
