lowercase user and invitation emails (#12130)

### Solution

> After discussion with charles & weiko, we chose the long term
solution.
> 
> Fix FE to request checkUserExists resolver with lowercased emails
> Add a decorator on User (and AppToken for invitation), to lowercase
email at user (appToken) creation. ⚠️ It works for TypeOrm .save method
only (there is no user email update in codebase, but in future it
could..)
> Add email lowercasing logic in external auth controller
> Fix FE to request sendInvitations resolver with lowercased emails
> Add migration command to lowercase all existing user emails and
invitation emails

> For other BE resolvers, we let them permissive. For example, if you
made a request on CheckUserExists resolver with uppercased email, you
will not found any user. We will not transform input before checking for
existence.

[link to comment
](https://github.com/twentyhq/twenty/pull/12130#discussion_r2098062093)

### Test 🚧 
- sign-in and up from main subdomain and workspace sub domain > Google
Auth (lowercased email) ✔️ | Microsoft Auth (uppercased email ✔️ &
lowercased email) | LoginPassword (uppercased email ✔️& lowercased
email✔️)
- invite flow with uppercased and lowercased ✔️
- migration command + sign-in ( former uppercased microsoft email ✔️) /
sign-up ( former uppercased invited email ✔️)

closes https://github.com/twentyhq/private-issues/issues/278, closes
https://github.com/twentyhq/private-issues/issues/275, closes
https://github.com/twentyhq/private-issues/issues/279

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

@@ -1,7 +1,10 @@
 import { Field, ObjectType } from '@nestjs/graphql';
 
 import { BeforeCreateOne, IDField } from '@ptc-org/nestjs-query-graphql';
+import { isDefined } from 'twenty-shared/utils';
 import {
+  BeforeInsert,
+  BeforeUpdate,
   Column,
   CreateDateColumn,
   Entity,
@@ -78,6 +81,14 @@ export class AppToken {
   @UpdateDateColumn({ type: 'timestamptz' })
   updatedAt: Date;
 
+  @BeforeInsert()
+  @BeforeUpdate()
+  formatEmail?() {
+    if (isDefined(this.context?.email)) {
+      this.context.email = this.context.email.toLowerCase();
+    }
+  }
+
   @Column({ nullable: true, type: 'jsonb' })
   context: { email: string } | null;
 }