refactor(server): test fixtures (#3491)

server/test/fixtures/file.stub.ts

@@ -0,0 +1,12 @@
+export const fileStub = {
+  livePhotoStill: Object.freeze({
+    originalPath: 'fake_path/asset_1.jpeg',
+    checksum: Buffer.from('file hash', 'utf8'),
+    originalName: 'asset_1.jpeg',
+  }),
+  livePhotoMotion: Object.freeze({
+    originalPath: 'fake_path/asset_1.mp4',
+    checksum: Buffer.from('live photo file hash', 'utf8'),
+    originalName: 'asset_1.mp4',
+  }),
+};