ios – Add events to the shared / subscribed calendar from your mobile?

My workplace has a shared calendar that we use to add customer reservations.

The server is

I have the calendar added as calendar subscribed in the Apple Calendar application on my iPhone as well as on my iPad, and I have it also configured on my PC through Outlook.

At this time, if I want to add a new client appointment to the calendar, I can only do it on my PC through Outlook. It seems that I can not add events through the native Calendar app on iOS.

Is there an alternative solution to be able to add appointments from my phone or iPad? The ideas I have had are:

Add the calendar as a normal calendar account on my iOS devices, but I do not know if that is possible.
Add the calendar to a third-party application that can create events.
Write a script that can publish an event in the calendar.
Any idea to someone?