The callers of startAudit and beginRankCheckRun were forwarding the
incoming billingCustomer object directly into workflow.create params.
At runtime the object can be an EnsuredUserContext with extra fields
beyond BillingCustomerContext, which pollutes the workflow instance's
persisted params payload. Explicitly pick the four required fields so
only the intended data is serialized into the workflow.
INTERNAL_ERROR was showing "An unexpected error occurred" to users and
triggering PostHog error monitoring for expected validation cases
(duplicate domain+country, max configs reached).
