[fix] Unable to create new CalDav calendar using the provided instructions

## Describe the bug
**Description:**
The instructions to [create new calendars in the CalDav FAQ](https://forwardemail.net/en/faq#do-you-support-calendars-caldav) do not work. I am unable to create new calendars using the provided instructions, however I am able to create new calendars in certain CalDav clients using their "create" method.

**Context:**
It may be relevant that the domain I am using has a catch-all alias enabled, but tbc I am using one and only one alias for all calendars.

## Actual behavior
The instructions suggest that to create new calendars, I should subscribe to a new calendar at the following URL, `https://caldav.forwardemail.net/dav/principals/calendar-name`, where `calendar-name` is the name of the new Calendar to be created. **This operation fails, and no calendar is created.**

However, when I authenticate and discover my available calendars at `https://caldav.forwardemail.net`, I notice each calendar URL is of the format:
```
https://caldav.forwardemail.net/dav/me@mydomain.net/44314b5f-9daa-4898-84bc-ad2da4b15757/
```

Additionally, when I create a new calendar using the "create" operation in another client (DAVx5), I am able to create a new calendar. Now, when I discover my available calendars at `https://caldav.forwardemail.net`, I see two calendars with unique UUIDs instead of my provided calendar name:
```
https://caldav.forwardemail.net/dav/me@mydomain.net/44314b5f-9daa-4898-84bc-ad2da4b15757/
https://caldav.forwardemail.net/dav/me@mydomain.net/87792b5f-0aad-7788-b48c-75751aadd2b4/
```

## Expected behavior

I expect a new calendar to be created. I suspect the documentation is just out of date.

## Checklist

- [x] I have searched through GitHub issues for similar issues.
- [x] I have completely read through the README and documentation.
- [x] I have tested my code with the latest version of Node.js and this package and confirmed it is still not working.