Add Gotify notification support.

[HellStorm666]

Please add Gotify support.
A great, free and open, notification system that is self hostable, docker compatible and works on Windows, Apple and Android devices.

I tried to use the HTTP option for the notification, but that only gave 400 error's.

What Gotify needs:
curl or POST methode.
$ curl "https://push.example.de/message?token=<apptoken>" -F "title=my title" -F "message=my message" -F "priority=5"
$ http -f POST "https://push.example.de/message?token=<apptoken>" title="my title" message="my message" priority="5"

as variable fields you need:
the server addres (http(s)://push.example.de)
API/app token

The whole POST message should be:
"https://push.example.de/message?token=<apptoken>" title="my title" message="my message" priority="5"

For extra info see: https://gotify.net/docs/pushmsg

[HellStorm666]

Ok, did some fiddeling with the HTTP methode and found the solution (howerver, I still would like a official solution).

At URL/Action you need to fill in the url with token. eg https://push.example.de/message?token=SDFt4f4ffsh
At POST Data you need to fill in:
{
"message": "#MESSAGE",
"priority": #PRIORITY,
"title": "#SUBJECT"
}

So including the { and }
Mark that #PRIORITY does not need " " around it, but #MESSAGE and #SUBJECT do.