Upload a supporting document to a facility workflow

Uploads a new file as a supporting document and appends it to the facility credentialing workflow's supporting documents list. When to use: Use to add a single supporting document without affecting existing documents. To replace the entire supporting documents list, use PUT /facility-credentialing-workflows/{workflowId}/supporting-documents. For attachments scoped to a specific section row rather than the whole workflow, use POST /facility-credentialing-workflows/{workflowId}/attachments. Request: Multipart form data. Fields: file (binary, required), fileType (required), state (optional), expirationDate (optional). Side effects: File is stored in Cloud Storage. Returns: 201 Created with the created supporting document record.