Exports a specified avatar.

The endpoint works the following way:

1. You send a request to the /exports/new endpoint.
   • If this version of avatar wasn't exported yet, the response will contain status='pending' and the export task will be created. The url will be null.
   • If it was successfully exported previously, the response will contain status='ready' and url will contain a link to the result. The URL is temporary and can only be used to download model to your servers. Don't store it to the database. <!-- * If the `wait=true` query parameter is present, the response will contain `status='ready'` and the `url` will provide a link to the result. Note that a hard timeout (60 seconds) is applied. We recommend using this feature for convenience only. If you need robustness, switch to webhooks. -->
2. If the task was created on step 1, on its completion avaturn will send an export.ready webhook, which will contain a temporary link to the export result.

NOTE: Behavior of this endpoint for avatars created by direct photo upload and not yet opened via browser UNDEFINED and can be changed in the future. Set customization via corresponding endpoint to get predictable behaviour.