Implement Appointment Scheduling Feature for Nextcloud Calendar

Is your feature request related to a problem? Please describe.

Currently, Nextcloud Calendar lacks a seamless method for creating and sharing appointment schedules directly from the calendar interface. Users often find it cumbersome to manage appointments efficiently without an integrated scheduling tool. This limitation can lead to confusion and extra administrative work, especially for those used to the functionality offered by platforms like Google Workspace.

Describe the solution you'd like

I would like to see an integrated feature in Nextcloud Calendar that allows users to:

1. Create a new appointment schedule directly within the calendar.
2. Enter details for the appointment such as date, time, and description.
3. Generate and share a reservation page link with others directly from the event in the calendar interface.
4. Display all reserved appointments automatically in the user’s calendar.
5. Send automatic calendar invitations via email to both the organizer and the attendees once an appointment is scheduled.

This feature should mimic the user-friendly process found in Google Workspace's appointment scheduling system, providing a streamlined and efficient way to handle appointments directly from the Nextcloud Calendar.

Describe alternatives you've considered

As an alternative, integrating third-party scheduling tools via plugins or APIs has been considered. However, this often requires additional configuration and maintenance, and might not provide as seamless an experience as a native feature.

Additional context

The inspiration for this feature comes from the appointment scheduling functionality provided by Google Workspace, which simplifies the process of managing appointments. You can see more about this feature here: [[Google Workspace Appointment Scheduling]([https://workspace.google.com/intl/de/resources/appointment-scheduling/].

This feature would significantly enhance the usability and efficiency of the Nextcloud Calendar for all users, particularly those in a professional or organizational context where scheduling is frequent.

Start with the issue description and its five requested capabilities, then review the linked Google Workspace reference for context. Identify the calendar entry points, reservation flow, invitation handling, and relevant tests before implementation; the work is done when appointment schedules can be created, shared, reserved, displayed, and emailed as described.