Add sessionHolding template, unique 8-digit codes, reason slot for sessionCancelled, and disable unused notifications

utils/uniqueCode.js

@@ -0,0 +1,30 @@
+'use strict';
+
+const crypto = require('crypto');
+
+const MIN_CODE = 10000000;
+const MAX_CODE = 100000000;
+
+/** Generate a random 8-digit numeric string (10000000–99999999). */
+const generateCode = () => String(crypto.randomInt(MIN_CODE, MAX_CODE));
+
+/**
+ * Allocate a unique code for a Mongoose model field.
+ * Retries on collision up to maxAttempts times.
+ */
+const generateUniqueCode = async (Model, field = 'uniqueCode', maxAttempts = 24) => {
+  if (!Model) throw new Error('Model is required to generate a unique code');
+
+  for (let attempt = 0; attempt < maxAttempts; attempt += 1) {
+    const code = generateCode();
+    const exists = await Model.exists({ [field]: code });
+    if (!exists) return code;
+  }
+
+  throw new Error(`Could not generate a unique ${field} after ${maxAttempts} attempts`);
+};
+
+module.exports = {
+  generateCode,
+  generateUniqueCode
+};