Create agent

curl --request POST \
  --url https://api.us.poly.ai/v1/agents \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "name": "<string>",
  "responseSettings": {
    "greeting": "<string>",
    "languageCode": "en-GB"
  },
  "voiceSettings": {
    "voiceId": "<string>"
  },
  "agentId": "<string>",
  "llmSettings": {
    "modelId": "<string>"
  }
}
'

{
  "accountId": "<string>",
  "agentId": "<string>",
  "agentName": "<string>",
  "createdAt": "<string>",
  "updatedAt": "<string>",
  "branchCount": 123
}