BYOM webhooks name the provider that rejected your credential
A byom.request_failed webhook event reported the primary provider and model
for every failure, also when the fallback provider ran. The event now names the
provider and model that produced the failure, and a rejected credential now
reports BYOM_CREDENTIALS_INVALID. Ingestion no longer retries a request that
a provider rejected because of the credential, so the failure reaches you on the
first attempt.