MC-39521: Random deadlocks during setting email sent flag

Author: Viktor Kopin

app/code/Magento/Sales/Model/EmailSenderHandler.php

@@ -132,8 +132,9 @@ public function sendEmails()
                 /** @var \Magento\Sales\Model\AbstractModel $item */
                 foreach ($entityCollection->getItems() as $item) {
                     if ($this->emailSender->send($item, true)) {
-                        $this->entityResource->save(
-                            $item->setEmailSent(true)
+                        $this->entityResource->saveAttribute(
+                            $item->setEmailSent(true),
+                            'email_sent'
                         );
                     }
                 }

app/code/Magento/Sales/Test/Unit/Model/EmailSenderHandlerTest.php

@@ -100,7 +100,7 @@ protected function setUp(): void
             false,
             false,
             true,
-            ['save']
+            ['saveAttribute']
         );
 
         $this->entityCollection = $this->getMockForAbstractClass(
@@ -252,7 +252,7 @@ public function testExecute($configValue, $collectionItems, $emailSendingResult)
 
                     $this->entityResource
                         ->expects($this->once())
-                        ->method('save')
+                        ->method('saveAttribute')
                         ->with($collectionItem);
                 }
             }