ThirdPartyServices: SetContactMethods for setting, enable/disable

replace AddContactMethods with a more generalised SetContactMethods,
which can set (or leave alone) contact method addresses/names/ids and
set (or leave alone) contact preferences. A little awkward to use, but
works everywhere, and now a bunch of Jellyseerr integration features are
present for Ombi (which they should've been anyway).

matrix.go

@@ -64,6 +64,16 @@ var matrixFilter = mautrix.Filter{
 	},
 }
 
+func EmptyMatrixUser() *MatrixUser {
+	return &MatrixUser{
+		RoomID:     "",
+		UserID:     "",
+		Lang:       "",
+		Contact:    false,
+		JellyfinID: "",
+	}
+}
+
 func (d *MatrixDaemon) renderUserID(uid id.UserID) id.UserID {
 	if uid[0] != '@' {
 		uid = "@" + uid