chore: Adds a users.uuid column (#24659)

* chore: Adds a users.uuid column

* Add uuid backfill

* Remove backfill due to possible locking issues

* feat: Add batched UUID backfill to prevent database locking

Implements a batched approach for backfilling UUIDs on existing users:
- Processes 1000 rows at a time to avoid table locks
- Uses FOR UPDATE SKIP LOCKED to prevent blocking other transactions
- Includes small delays between batches (10ms) to allow other operations
- Logs progress every 10,000 rows for monitoring

This approach is safe for production databases with millions of users.

Co-Authored-By: alex@cal.com <me@alexvanandel.com>

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: sean-brydon <55134778+sean-brydon@users.noreply.github.com>

packages/prisma/migrations/20251023133244_add_user_uuid_column/migration.sql

@@ -0,0 +1,48 @@
+/*
+  Warnings:
+
+  - A unique constraint covering the columns `[uuid]` on the table `users` will be added. If there are existing duplicate values, this will fail.
+
+*/
+-- AlterTable
+ALTER TABLE "public"."users" ADD COLUMN     "uuid" UUID;
+
+-- CreateIndex
+CREATE UNIQUE INDEX "users_uuid_key" ON "public"."users"("uuid");
+
+-- Backfill UUIDs in batches to avoid table locking on large datasets
+-- Uses FOR UPDATE SKIP LOCKED to prevent blocking other transactions
+-- Processes 1000 rows at a time with small delays between batches
+DO $$
+DECLARE
+  batch_size INT := 1000;
+  rows_updated INT;
+  total_updated INT := 0;
+BEGIN
+  LOOP
+    WITH batch AS (
+      SELECT id
+      FROM "public"."users"
+      WHERE uuid IS NULL
+      LIMIT batch_size
+      FOR UPDATE SKIP LOCKED
+    )
+    UPDATE "public"."users"
+    SET uuid = gen_random_uuid()
+    FROM batch
+    WHERE "public"."users".id = batch.id;
+    
+    GET DIAGNOSTICS rows_updated = ROW_COUNT;
+    total_updated := total_updated + rows_updated;
+    
+    EXIT WHEN rows_updated = 0;
+    
+    PERFORM pg_sleep(0.01);
+    
+    IF total_updated % 10000 = 0 THEN
+      RAISE NOTICE 'Updated % users with UUIDs', total_updated;
+    END IF;
+  END LOOP;
+  
+  RAISE NOTICE 'Completed: Updated % total users with UUIDs', total_updated;
+END $$;

packages/prisma/schema.prisma

@@ -347,6 +347,7 @@ model TravelSchedule {
 // It holds Personal Profiles of a User plus it has email, password and other core things..
 model User {
   id                  Int                  @id @default(autoincrement())
+  uuid                String?              @unique @default(uuid()) @db.Uuid
   username            String?
   name                String?
   /// @zod.import(["import { emailSchema } from '@calcom/lib/emailSchema'"]).custom.use(emailSchema)