Invoke a model with routing

curl --request POST \
  --url https://api-sandbox.featherhq.com/v1/model-router/invoke \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "messages": [
    {
      "role": "<string>",
      "content": "<string>"
    }
  ],
  "router_config_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "config_overrides": {},
  "session_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "smart_routing": false
}
'

{
  "content": "<string>",
  "model_identifier": "<string>",
  "provider": "<string>",
  "input_tokens": 123,
  "output_tokens": 123,
  "total_tokens": 123,
  "input_cost_usd": 123,
  "output_cost_usd": 123,
  "total_cost_usd": 123,
  "latency_ms": 123,
  "tool_calls": [
    {}
  ],
  "routing_metadata": {
    "classifier_model": "<string>",
    "classifier_confidence": 123,
    "recommended_model": "<string>",
    "executed_model": "<string>",
    "candidate_chain": [
      "<string>"
    ],
    "reason": "<string>"
  },
  "parsed_output": {},
  "execution_engine": "pydantic_text",
  "cache_read_input_tokens": 0,
  "cache_creation_input_tokens": 0,
  "cache_hit": false,
  "route_decision_id": "<string>"
}