## Subscribe to notification topics

Subscribe an email address to one or more notification topics for this merchant.
The email will receive notifications when events related to those topics occur.

This endpoint supports both create and update operations:
- **Create**: When no subscriptions exist for the email+merchant combination
- **Update**: When subscriptions exist, it will delete all existing subscriptions for that email+merchant and create new ones

You can subscribe to multiple topics at once by providing an array of topic IDs.
The language parameter determines the language of the notifications sent to this email.

This endpoint requires authentication and will create email subscriptions for the specified
merchant and notification topics.

## Endpoint signature

```http
POST https://api.reservepay.com/merchants/subscribe-to-topics HTTP/1.1
Content-Type: application/json
Accept: application/json
Authorization: Bearer <token>

{
  email: string,
  language: string,
  notification_topic_ids: array,
}
```

Returns: boolean

## Request arguments

### `email` (string)

**Required**. The email address to subscribe to the notification topics.

### `language` (string)

**Required**. The language for notifications sent to this email address (e.g., "en", "es", "fr").

Allowed values:

- `en`
- `th`

### `notification_topic_ids` (array)

**Required**. Array of notification topic IDs to subscribe to. You can subscribe to multiple topics at once.

## Errors specific to this endpoint

### `NOT_FOUND`

One or more notification topics with the specified IDs could not be found.

## 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This commonly happens when using an outdated SDK or when the API version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.