Modify instance configuration

curl --request POST \
  --url https://api.thundercompute.com:8443/instances/{instance_id}/modify \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "cpu_cores": 123,
  "gpu_type": "<string>",
  "num_gpus": 123,
  "disk_size_gb": 123
}'

{
  "identifier": "<string>",
  "instance_name": "<string>"
}