Extended properties of the google calendar events get erased

[kewisch]

Discussed in #736

^{Originally posted by NotGonnaGetMe March 27, 2024}
I am using the extended properties of the Google calendar events which I synchronize with Thunderbird. Everything is fine until I dismiss an event notification in Thunderbird, at that moment all of my extended properties are erased and replaced with X-MOZ-LASTACK private property. I assume that the plugin doesn't preserve other extended properties but this one. I hope this can be fixed

[RedwanFox]

I think it's the same issue or related #156 - event attendees are also erased on dismiss