Changes to Ingest External Usage

added the optional property code to the response with the 422 status

added the new optional request property events/items/reasoning_tokens

removed the request property events/items/reasoning_tokens

added the new optional request property events/items/reasoning_tokens

api operation id ingest_external_usage_api_v1_usage_external_events_post removed and replaced with usage-ingest_external_usage

endpoint added