mattermost: disable analytics & telemetry

note that this ALSO disables the security alert features of mattermost [1],
which would send us alerts in case of security updates for our current
mattermost version. I have disabled it since it would send information
about our instance (including e.g. the current number of active users) to
mattermost every 24 hours.

Since we now essentially maintain our own set of mattermost packages, I
recommend at least some of us subscribe to the mattermost release blog [2],
and manually update the mattermost sources in `/pkgs/mattermost` as required
(I have done so already). The release blog is also available as an rss feed [3].

[1] https://docs.mattermost.com/administration/telemetry.html#security-update-check-feature
[2] https://mattermost.com/blog/category/releases
[3] https://mattermost.com/blog/category/releases/rss

hosts/hainich/services/mattermost.nix

@@ -54,6 +54,7 @@
             EnableSVGs = true;
             EnableLaTeX = true;
             ThreadAutoFollow = true;
+            EnableSecurityFixAlert = false;
           };
           TeamSettings = {
             EnableTeamCreation = true;
@@ -66,8 +67,8 @@
           LogSettings = {
             EnableConsole = true;
             ConsoleLevel = "ERROR";
-            EnableDiagnostics = true;
-            EnableWebhookDebugging = true;  
+            EnableDiagnostics = false;
+            EnableWebhookDebugging = false;
           };
           NotificationLogSettings = {
             EnableConsole = true;