TYPO3 Core

<meta name="generator" content="TYPO3 CMS" />
<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover" />
<meta name="robots" content="index,follow" />
...
<meta property="og:image:type" content="image/png" />
<meta property="og:title" content="IN.DIE.musik e.V." />
<meta name="twitter:card" content="summary" />
<meta name="twitter:site" content="@InDieMusik" />

https://github.com/TYPO3/typo3/blob/main/typo3/sysext/core/Classes/MetaTag/AbstractMetaTagManager.php#L226-L239

$metaTags[] = '<meta ' .
  htmlspecialchars($nameAttribute) . '="' . htmlspecialchars($property) . '" ' .
  htmlspecialchars($contentAttribute) . '="' . htmlspecialchars($propertyItem['content']) . '" />';