## Prepare payment link batch

Starts validating the uploaded payment link xlsx in the background. The batch moves from
`created` to `preparing`. When validation finishes, the batch becomes `prepared` and a
preview JSON file is attached.

Call this after uploading the file to the `upload_url` returned by `create-payment-link-batch`.
Poll `find-batch` until the status is `PREPARED` (or `CREATED` again if the spreadsheet is invalid).

## Endpoint signature

```http
POST https://api.reservepay.com/merchants/prepare-payment-link-batch HTTP/1.1
Content-Type: application/json
Accept: application/json
Authorization: Bearer <token>

{
  batch_id: string,
}
```

Returns: object

## Request arguments

### `batch_id` (string)

**Required**. The unique identifier of the batch (`bat_...`).

## Response attributes

### `batch_id` (string)

**Always present**. The unique identifier of the batch.

### `type` (string)

**Always present**. The type of records in this batch.

Possible values:

- `PAYMENT_LINK`
- `PAYOUT`

### `status` (string)

**Always present**. The current processing status of the batch.

Possible values:

- `CREATED`
- `PREPARING`
- `PREPARED`
- `PROCESSING`
- `COMPLETED`

### `output_url` (string)

_Nullable_. The URL to download the result xlsx file. Present when the batch has completed.

### `preview_url` (string)

_Nullable_. The URL to download the validated drafts JSON. Included after prepare has completed.

### `error_message` (string)

_Nullable_. The failure reason when prepare or processing did not complete. Included when a background job failed.

### `created_at` (number)

**Always present**. The timestamp when the batch was created.

## Errors specific to this endpoint

### `NOT_FOUND`

The batch was not found, or the input file has not been uploaded yet.

### `INVALID_STATE`

The batch is not in the created state.

## Errors common to all endpoints

### `UNHANDLED_ERROR`

This error occurs when the server encounters an unexpected internal error that
it cannot handle gracefully. This typically happens due to bugs, infrastructure
issues, or edge cases that weren't anticipated during development.

### `INVALID_ARGUMENTS`

This error occurs when the request contains invalid or missing parameters.
Common cases include missing required fields, or values that don't match the
expected format or type.

### `BAD_VERSION`

This error occurs when making requests to an API version that does not exist.
This commonly happens when using an outdated SDK or when the API version
specified in the request URL is incorrect.