Generate a Provider Summary Verification document for a workflow

Generates a Provider Summary Verification (PSV) document for the credentialing workflow identified by id and stores it in cloud storage. Use this endpoint to produce or refresh the PSV; use GET /credentialing-workflows/{id}/latest-psv-pdf to retrieve the path of the most recently generated PSV without regenerating it. This endpoint is authenticated via API key (not JWT) when invoked from Cloud Tasks. The optional triggeringEventId parameter associates the generation with a specific timeline event for step-tracking purposes; omit it for direct invocations. Returns a GeneratePsvResponse object containing the URL of the generated PSV document.