Upload a certificate for a customer

Upload a certificate on a customer's behalf, as multipart/form-data with the file in the file part, to cover their uncertified jurisdictions. The file must be a PDF, PNG or JPG and at most 10 MB. Creates one validation job per uncovered exemption and returns 202 with an uploadSessionId; poll GET /exemptions/missing-certificates/{customerId}/upload-status/{uploadSessionId} for per-jurisdiction results. Scoped to one organization the same way as the list. Returns 404 if the customer has no uncovered exemptions in an organization your credential can access. A free plan is refused with 403 PLAN_UPGRADE_REQUIRED. A paid plan without exemption certificate management is refused with 403 FORBIDDEN.