This allows us to add it to other Dialogs

- Gnome does not support body-markup
- Title should not be escaped

DBus does not support nullable types like GLib.Variant('ms', 'test')

- This makes type annotations easier

- Add dedicated methods for some events
- Add type annotations
- Events: Use JID object instead of string

Code regarding blocking signed in notifications, because we don’t
show these notifications anymore

nbxmpp does not support client certificates anymore