Add getUserIdentifier method to match SF6 new interface

config.xml

@@ -2,7 +2,7 @@
 <module>
     <name>keycloak_connector_demo</name>
     <displayName><![CDATA[Keycloak OAuth2 connector demo]]></displayName>
-    <version><![CDATA[1.0.3]]></version>
+    <version><![CDATA[1.0.4]]></version>
     <description><![CDATA[Demo module of how to use Keycloak as OAuth2 Authentication Server for the new API]]></description>
     <author><![CDATA[PrestaShop]]></author>
     <tab><![CDATA[]]></tab>

keycloak_connector_demo.php

@@ -34,7 +34,7 @@ public function __construct()
     {
         $this->name = 'keycloak_connector_demo';
         $this->displayName = 'Keycloak OAuth2 connector demo';
-        $this->version = '1.0.3';
+        $this->version = '1.0.4';
         $this->author = 'PrestaShop';
         $this->description = 'Demo module of how to use Keycloak as OAuth2 Authentication Server for the new API';
         $this->need_instance = 0;

src/OAuth2/KeyCloakUser.php

@@ -56,6 +56,11 @@ public function getUsername(): string
         return $this->username;
     }
 
+    public function getUserIdentifier(): string
+    {
+        return $this->username;
+    }
+
     public function eraseCredentials(): void
     {
     }