Google sitemap endpoint

[Jotschi]

Add REST endpoint which can be used to generates a google sitemap xml file.

[Jotschi]

Tasks:

• [ ] Changelog
• [ ] Documentation
• [ ] Endpoint implementation
• [ ] Add content parser to identify linked nodes
• [ ] Add edge between NGFC and Node which represents the link

[Jotschi]

Open Spec:

• https://www.sitemaps.org/de/protocol.html#urldef

Language Variant Handling:

• https://support.google.com/webmasters/answer/2620865?hl=en

Image / Video Handling:

• https://support.google.com/webmasters/answer/178636
• https://www.terramedia.de/an-der-naechsten-datenkreuzung-links-die-google-sitemap/