refactor: strengthen upload boundary types

lib/upload-request.ts

@@ -0,0 +1,28 @@
+export type DriveAction = 'new' | 'replace'
+
+interface StagingRequestBody {
+  stagingId: string
+}
+
+interface DriveRequestBody extends StagingRequestBody {
+  action: DriveAction
+}
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === 'object' && value !== null
+}
+
+export function parseStagingRequestBody(value: unknown): StagingRequestBody {
+  if (!isRecord(value) || typeof value.stagingId !== 'string' || value.stagingId.trim() === '') {
+    throw new Error('stagingId manquant')
+  }
+
+  return { stagingId: value.stagingId }
+}
+
+export function parseDriveRequestBody(value: unknown): DriveRequestBody {
+  const { stagingId } = parseStagingRequestBody(value)
+  const action = isRecord(value) && value.action === 'replace' ? 'replace' : 'new'
+
+  return { stagingId, action }
+}