curl --request POST \
  --url https://shardcloud.app/api/apps/{app_id}/domain \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "custom_domain": "<string>"
}'

{
  "message": "<string>",
  "custom_hostname": {},
  "cname": "<string>"
}