How to make integration with mail - calendar and yandex-calendar, like google?

Question

Programming

Guys, I have a question. There is a plugin addtocalendar.com, which allows you to send events to users via icalendar google, yahoo, i.e. the user comes under the uchetka and to it saobyt is added. This is what I did. The problem is that now the customer wants to be able to add an event through the web interface, like Google, but in mail.ru Calendar and Yandex Calendar. My question is, is there anyway to do this? I looked through all the docks of Yandex and mail.ru, they have the ability to view the event by other people, and there is no functionality, well, or I didn’t find it, adding, for example, an event to Vasya Pupkin that his subscription has ended. How can this be done at all? I have already generated a file in the caldav format, but the user will not first download this event and then import it to his calendar. ((