Symfony Doctrine two keys for different purposes, one AUTO_INCREMENT - php

Question

I'm new to Symfony and Doctrine and using the latest versions, am trying to create a Model with two key fields (attributes) for different purposes. $id is not the Primary Key but is AUTO_INCREMENT in MySQL/MariaDB. $key is string length=100 mapped to CHAR[100] and is the primary key and #ORM\Id. Even though this is what I'm trying to do, I don't think it's a supported configuration. I want to be able to merge() using key but also want to have the AI column for references (joining) because in part as I think it will have better performance, and even if not I want it anyway :) The thing is the data source which I use to populate may send multiple objects with the same key in which case I want them to persist to the same record, the last object the last to update the db, no duplicate keys.
I read somewhere, to use the DB implementation of AI and on non primary key, I may have to write a custom Hydrator. I have little idea what files to create and where to put them, and what mapping I have to do, or how exactly to do it. Hope someone can help.
<?php
// src/Entity/View.php
namespace App\Entity;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity(repositoryClass="App\Repository\ViewRepository")
*/
class View
{
/**
* #ORM\Column(type="integer", name="created_by")
*/
private $created_by;
/**
* #ORM\Column(type="integer", name="updated_by")
*/
private $updated_by;
/**
* #ORM\Column(type="bigint", name="id")
* #ORM\GeneratedValue(strategy="IDENTITY")
*/
private $id;
/**
* #ORM\Id
* #ORM\Column(type="string", length=100, name="`key`")
*/
private $key;
/**
* #ORM\Column(type="json", name="`value`")
*/
private $value;
public function getCreatedBy()
{
return $this->created_by;
}
public function setCreatedBy($value)
{
$this->created_by = $value;
}
public function getUpdatedBy()
{
return $this->updated_by;
}
public function setUpdatedBy($value)
{
$this->updated_by = $value;
}
public function getId()
{
return $this->id;
}
public function setId($value)
{
$this->id = $value;
}
public function getKey()
{
return $this->key;
}
public function setKey($value)
{
$this->key = $value;
}
public function getValue()
{
return $this->value;
}
public function setValue($value)
{
$this->value = $value;
}
}
/* View */
CREATE TABLE IF NOT EXISTS `View` (
updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
created_by INT UNSIGNED NOT NULL,
updated_by INT UNSIGNED NOT NULL,
id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
`key` CHAR(100) NOT NULL,
`value` JSON NOT NULL,
PRIMARY KEY PK_VIEW (`key`),
UNIQUE KEY UQ_VIEW (id)
) CHARSET = latin1;
$entity = new View();
$entity->setCreatedBy(0);
$entity->setUpdatedBy(0);
$entity->setKey($messageId);
$entity->setValue($json);
$entityManager = $this->getDoctrine()->getManager();
$entityManager->merge($entity);
$entityManager->flush();