[DOC IMPROVE] Add special case for cmdb.category with network connector assigment

## Affected Article

- Link to the article: https://kb.i-doit.com/en/i-doit-add-ons/api/methods/cmdb.category.html

## Suggested Improvements

Add special handling section and add for example the handling for adding network connection.
To assign a Network Port with "assigned_connector" attribute, it needs the ID of the referenced Cabling > Connector 