Set a unique constraint on email table in users #7180 (#7184)

Link to issue - https://github.com/twentyhq/twenty/issues/7180

File changed -
twenty/packages/twenty-server/src/engine/core-modules/user/user.entity.ts

---------

Co-authored-by: subham sharma <subham.sharma@smartbear.com>
Co-authored-by: Félix Malfait <felix@twenty.com>

packages/twenty-server/src/engine/core-modules/user/user.entity.ts

@@ -9,7 +9,8 @@ import {
   OneToMany,
   PrimaryGeneratedColumn,
   Relation,
-  UpdateDateColumn,
+  Unique,
+  UpdateDateColumn
 } from 'typeorm';
 
 import { UUIDScalarType } from 'src/engine/api/graphql/workspace-schema-builder/graphql-types/scalars';
@@ -27,6 +28,7 @@ registerEnumType(OnboardingStatus, {
 
 @Entity({ name: 'user', schema: 'core' })
 @ObjectType('User')
+@Unique('UQ_USER_EMAIL', ['email', 'deletedAt'])
 export class User {
   @IDField(() => UUIDScalarType)
   @PrimaryGeneratedColumn('uuid')