Overriding discriminator mapping on join table - doctrine-orm

Question

The project works with multiple user logins (plumber, builder), the relevant information for each entity is saved in their respective tables. The structure for them is supplied below.
We've been storing the information for suppliers and have now gathered a few hundred entries. Suppliers are now requiring a login to access the system.
The current flow with the discriminator map is it creates an entry in the Users table and then saves in the respective user type table with the id being that of the user.id.
User.id = 5 => plumber.id = 5
User.id = 6 => builder.id = 6
User.id = 7 => plumber.id = 7
Suppliers have had their own table with their own incrementing ids which would cause clashes with the DiscriminatorMap(). Is there a way to have suppliers be unique and connect on a supplier.user_id instead of supplier.id, like the other tables?
<?php
namespace Project\Entities;
abstract class BaseEntity
{
public static $idCol = 'id';
public static $joins = [];
public static $orderBy = [];
}
?>
<?php
namespace Project\Entities;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\ORM\Mapping AS ORM;
use Illuminate\Contracts\Auth\Authenticatable;
use Illuminate\Database\Eloquent\Model;
/**
* #ORM\Entity(repositoryClass="Project\Repositories\User\UserRepository")
* #ORM\Table(name="user")
* #ORM\InheritanceType("JOINED")
* #ORM\DiscriminatorColumn(name="type", type="string")
* #ORM\DiscriminatorMap({"user"="User", "plumber"="Plumber", "builder"="Builder"})
* #ORM\HasLifecycleCallbacks()
*/
class User extends BaseEntity implements Authenticatable
{
use \LaravelDoctrine\ORM\Auth\Authenticatable;
use \Project\Entities\Traits\HasContactDetails;
const TYPE_USER = "user";
const TYPE_PLUMBER = "plumber";
const TYPE_BUILDER = "builder";
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
* #var int
*/
protected $id;
/**
* #ORM\Column(type="string", unique=true, nullable=false)
* #var string
*/
protected $login;
/**
* #ORM\Column(type="text")
* #var string
*/
protected $password;
/**
* #return int
*/
public function getId() {
return $this->id;
}
/**
* #return string
*/
public function getLogin() {
return $this->login;
}
/**
* #param string $login
*/
public function setLogin($login) {
$this->login = $login;
}
public function getAuthPassword() {
return $this->password;
}
/**
* Encrypt password when inserting
* #ORM\PrePersist
*/
public function onPrePersist() {
$this->encryptPassword();
}
/**
* Encrypt password when updating
* #ORM\PreUpdate
*/
public function onPreUpdate(\Doctrine\ORM\Event\PreUpdateEventArgs $event) {
if ($event->hasChangedField('password')) {
$this->encryptPassword();
}
}
/**
*
* #return string
*/
public function getType() {
if ($this instanceof \Project\Entities\Plumber) {
return self::TYPE_PLUMBER;
}
if ($this instanceof \Project\Entities\Builder) {
return self::TYPE_BUILDER;
}
return self::TYPE_USER;
}
public function getAuthIdentifierName() {
return "login";
}
.....
}
?>
User roles extending
<?php
namespace Project\Entities;
use Doctrine\ORM\Mapping AS ORM;
/**
* #ORM\Entity(repositoryClass="Project\Repositories\Plumber\PlumberRepository")
* #ORM\Table(name="plumber")
*/
class Plumber extends User
{
.....
}
?>
<?php
namespace Project\Entities;
use Doctrine\ORM\Mapping AS ORM;
/**
* #ORM\Entity(repositoryClass="Project\Repositories\Builder\BuilderRepository")
* #ORM\Table(name="builder")
*/
class Builder extends User
{
.....
}
?>
The current supplier entity.
<?php
namespace Project\Entities;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\ORM\Mapping AS ORM;
/**
* #ORM\Entity(repositoryClass="Project\Repositories\Supplier\SupplierRepository")
* #ORM\Table(name="supplier")
*/
class Supplier extends BaseEntity
{
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
* #var int
*/
protected $id;
/**
* #ORM\Column(type="string")
* #var string
*/
protected $name;
/**
* #ORM\ManyToOne(targetEntity="Region")
* #var Region
*/
protected $region;
public function getId() {
return $this->id;
}
public function getName() {
return $this->name;
}
public function getRegion() {
return $this->region;
}
public function setId($id) {
$this->id = $id;
}
public function setName($name) {
$this->name = $name;
}
/**
* #param Region $region
*/
public function setRegion($region) {
$this->region = $region;
}
.....
}
?>