I searched for how to add a calendar entry into Nextcloud or any way to use CalDAV to add a meeting. I did not find any nodes to do it. The one CalDAV node only pulls the meetings and does not have a way to create a meeting.
So, I created the below flow. You have to have a login and password in the Function node. It creates both the CalDAV data and the encoded auth. The http api node handles the connection and sending the data to nextcloud.
Sorry, I dont know how to write a node so if someone wants to use this to make a node for N8N, You have my permission to use anything here.