Add the ability to create new Customers with an already used e-mail

A same e-mail can only be used for several Customers as long as they are not linked to the same Mailbox.

src/Email.php

@@ -0,0 +1,31 @@
+<?php
+/*
+ SPDX-License-Identifier: AGPL-3.0-only
+ SPDX-FileCopyrightText: © 2024 Millions Missing FRANCE <info@millionsmissing.fr>
+ */
+
+namespace MillionsMissingFrance\FreescoutRestrictedCustomers;
+
+use Illuminate\Database\Eloquent\Model;
+use Watson\Rememberable\Rememberable;
+use App\Email as BaseEmail;
+
+class Email extends BaseEmail {
+	/**
+	 * Check if an Email already exists for a given Mailbox.
+	 *
+	 * @param Mailbox $mailbox
+	 * @param string  $email
+	 *
+	 * @return bool
+	 */
+	public static function alreadyExistsInMailbox($mailbox, $email) {
+		$emails_count = self
+			::whereHas('customer', function($query) use($mailbox) {
+				$query->where('mailbox_id', '=', $mailbox->id);
+			})
+			->where('email', $email)
+			->count();
+		return ( $emails_count != 0 );
+	}
+}

src/Http/Controllers/CrmController.php

@@ -7,7 +7,6 @@
 namespace MillionsMissingFrance\FreescoutRestrictedCustomers\Http\Controllers;
 
 use App\Conversation;
-use App\Email;
 use Modules\Crm\Entities\CustomerField;
 use Modules\Crm\Entities\CustomerCustomerField;
 use Validator;
@@ -16,6 +15,8 @@ use Illuminate\Http\Response;
 use Illuminate\Routing\Controller;
 use Modules\Crm\Http\Controllers\CrmController as BaseCrmController;
 use MillionsMissingFrance\FreescoutRestrictedCustomers\Customer;
+use MillionsMissingFrance\FreescoutRestrictedCustomers\Email;
+use MillionsMissingFrance\FreescoutRestrictedCustomers\Mailbox;
 
 class CrmController extends BaseCrmController {
 	public function createCustomer(Request $request) {
@@ -53,10 +54,11 @@ class CrmController extends BaseCrmController {
 
 		// Check email uniqueness.
 		$fail = false;
+		$mailbox = Mailbox::find($request->mailbox);
 		foreach ($request->emails as $i => $email) {
 			$sanitized_email = Email::sanitizeEmail($email);
 			if ($sanitized_email) {
-				$email_exists = Email::where('email', $sanitized_email)->first();
+				$email_exists = Email::alreadyExistsInMailbox($mailbox, $sanitized_email);
 
 				if ($email_exists) {
 					$validator->getMessageBag()->add('emails.'.$i, __('A customer with this email already exists.'));