Add unit tests for data file rotation utility functions

- Implement tests for writing data files with rotation, ensuring backups are created only on changes.
- Verify that old backups are rotated correctly and the maximum number of backups is maintained.
- Test restoration of backups while preserving the current state as a backup.
- Utilize Vitest for testing framework and manage temporary file storage during tests.

server/utils/members.js

@@ -2,6 +2,7 @@ import { promises as fs } from 'fs'
 import path from 'path'
 import { randomUUID } from 'crypto'
 import { encrypt, decrypt, encryptObject, decryptObject } from './encryption.js'
+import { writeDataFileWithRotation } from './data-file-rotation.js'
 
 // Handle both dev and production paths
 // nosemgrep: javascript.lang.security.audit.path-traversal.path-join-resolve-traversal.path-join-resolve-traversal
@@ -192,7 +193,7 @@ export async function writeMembers(members) {
   try {
     const encryptionKey = getEncryptionKey()
     const encryptedData = encryptObject(members, encryptionKey)
-    await fs.writeFile(MEMBERS_FILE, encryptedData, 'utf-8')
+    await writeDataFileWithRotation(MEMBERS_FILE, encryptedData, { encoding: 'utf-8' })
     return true
   } catch (error) {
     console.error('Fehler beim Schreiben der Mitgliederdaten:', error)