use internal QR code generator instead of googleapi service

composer.json

@@ -34,7 +34,8 @@
   "require": {
     "php": ">=5.6",
     "oxid-esales/oxideshop-metapackage-ce": "~6.0.3 || ~6.1.0",
-    "spomky-labs/otphp": "^8.3 || ^9.0"
+    "spomky-labs/otphp": "^8.3 || ^9.0",
+    "bacon/bacon-qr-code": "^1.0 || ^2.0"
   },
   "autoload": {
     "psr-4": {

src/Application/Model/d3totp.php

@@ -15,6 +15,10 @@
 
 namespace D3\Totp\Application\Model;
 
+use BaconQrCode\Renderer\Image\SvgImageBackEnd;
+use BaconQrCode\Renderer\ImageRenderer;
+use BaconQrCode\Renderer\RendererStyle\RendererStyle;
+use BaconQrCode\Writer;
 use D3\ModCfg\Application\Model\d3database;
 use D3\Totp\Application\Model\Exceptions\d3totp_wrongOtpException;
 use Doctrine\DBAL\DBALException;
@@ -138,7 +142,7 @@ class d3totp extends BaseModel
                 $this->totp = TOTP::create($seed ? $seed : $this->getSavedSecret());
                 $this->totp->setLabel($this->getUser()->getFieldData('oxusername')
                     ? $this->getUser()->getFieldData('oxusername')
-                    : null
+                    : ''
                 );
             }
             $this->totp->setIssuer(Registry::getConfig()->getActiveShop()->getFieldData('oxname'));
@@ -165,6 +169,21 @@ class d3totp extends BaseModel
         return $this->getTotp()->getQrCodeUri();
     }
 
+    /**
+     * @return string
+     */
+    public function getQrCodeElement()
+    {
+        /** @var ImageRenderer $renderer */
+        $renderer = oxNew(ImageRenderer::class,
+            oxNew(RendererStyle::class, 200),
+            oxNew(SvgImageBackEnd::class)
+        );
+        /** @var Writer $writer */
+        $writer = oxNew(Writer::class, $renderer);
+        return $writer->writeString($this->getTotp()->getProvisioningUri());
+    }
+
     /**
      * @return string
      */

src/Application/views/admin/tpl/d3user_totp.tpl

@@ -48,7 +48,7 @@
                                         [{oxmultilang ident="D3_TOTP_QRCODE"}] 
                                     </td>
                                     <td class="edittext">
-                                        <img src="[{$totp->getQrCodeUri()}]">
+                                        [{$totp->getQrCodeElement()}]
                                         [{oxinputhelp ident="D3_TOTP_QRCODE_HELP"}]
                                     </td>
                                 </tr>