Encapsulate SAP page layout

Author: Bellangelo

registries/_namespace/sap.md

@@ -5,17 +5,10 @@ description: Extensions created and used by SAP
 layout: default
 ---
 
-# <a href="..">{{ page.collection }}</a>
-
-## {{ page.slug }} - {{ page.description }}
-
-
+{% capture summary %}
 The `x-{{page.slug}}-` prefix is reserved for extensions created by SAP. These extensions are available for use by anyone.
 
 The official list of supported SAP extensions can be found in [SAP/openapi-specification](https://github.com/SAP/openapi-specification) repository.
+{% endcapture %}
 
-{% if page.issue %}
-### GitHub Issue
-
-* [#{{ page.issue }}](https://github.com/OAI/OpenAPI-Specification/issues/{{ page.issue }})
-{% endif %}
+{% include namespace-entry.md summary=summary %}