Add a planet type feature

Problem/Motivation

The Original Drupal Planet is an RRS aggregator that currently only allows articles about Drupal in English.

The "Planet Drupal" feature that we currently offer in the Drupal Centre in Germany, on the other hand, only aggregates the contributions that the UrserGroups in Germany provide on groups.drupal.org and, similar to planet.drupal.org, offers the possibility to retrieve this content as an RSS feed.

On the one hand, this is great, but on the other hand, it does not yet allow the application of sources that regularly publish news and articles about Drupal. That's why we should expand planet Drupal accordingly so that visitors to the Drupalcentre will be able to retrieve current articles and news about Drupal from the web, which are written in German, as an RSS feed and read them regularly with their favourite RSS reader on their preferred device.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes