nixos/mattermost: disable telemetry by default

We should disable telemetry but enable security update checks. Make both
controlable in the module without digging into settings.

Disabling telemetry also makes NixOS tests faster because the server
tries to send telemetry on first start.

nixos/modules/services/web-apps/mattermost.nix

@@ -202,6 +202,7 @@ let
       ListenAddress = "${cfg.host}:${toString cfg.port}";
       LocalModeSocketLocation = cfg.socket.path;
       EnableLocalMode = cfg.socket.enable;
+      EnableSecurityFixAlert = cfg.telemetry.enableSecurityAlerts;
     };
     TeamSettings.SiteName = cfg.siteName;
     SqlSettings.DriverName = cfg.database.driver;
@@ -233,7 +234,13 @@ let
     FileSettings.Directory = cfg.dataDir;
     PluginSettings.Directory = "${pluginDir}/server";
     PluginSettings.ClientDirectory = "${pluginDir}/client";
-    LogSettings.FileLocation = cfg.logDir;
+    LogSettings = {
+      FileLocation = cfg.logDir;
+
+      # Reaches out to Mattermost's servers for telemetry; disable it by default.
+      # https://docs.mattermost.com/configure/environment-configuration-settings.html#enable-diagnostics-and-error-reporting
+      EnableDiagnostics = cfg.telemetry.enableDiagnostics;
+    };
   } cfg.settings;
 
   mattermostConf = recursiveUpdate mattermostConfWithoutPlugins (
@@ -474,6 +481,26 @@ in
         '';
       };
 
+      telemetry = {
+        enableSecurityAlerts = mkOption {
+          type = types.bool;
+          default = true;
+          description = ''
+            True if we should enable security update checking. This reaches out to Mattermost's servers:
+            https://docs.mattermost.com/manage/telemetry.html#security-update-check-feature
+          '';
+        };
+
+        enableDiagnostics = mkOption {
+          type = types.bool;
+          default = false;
+          description = ''
+            True if we should enable sending diagnostic data. This reaches out to Mattermost's servers:
+            https://docs.mattermost.com/manage/telemetry.html#error-and-diagnostics-reporting-feature
+          '';
+        };
+      };
+
       environment = mkOption {
         type = with types; attrsOf (either int str);
         default = { };

nixos/tests/mattermost/default.nix

@@ -48,6 +48,7 @@ import ../make-test-python.nix (
               database = {
                 peerAuth = lib.mkDefault true;
               };
+              telemetry.enableSecurityAlerts = false;
               settings = {
                 SupportSettings.AboutLink = "https://nixos.org";
                 PluginSettings.AutomaticPrepackagedPlugins = false;