Attach a file

Links a previously uploaded file to an authorization as a supporting document. The file must be `ready` and must have `purpose = authorization_attachment`. One file can satisfy multiple required document types — list every type the file satisfies in `documentTypes`. Attaching a file recomputes `requirements`. When all document and answer blockers clear, the authorization moves to `requires_action` with `nextAction.type = continue_authorization`. Attachment writes never resume Collate processing on their own. When `status = requires_action`, call [Confirm an authorization](api:POST/v1/prior-authorizations/{authorization_id}/confirm) to advance the case. ## Returns Returns the updated authorization.