graylog-6_1: init at 6.1.8

Also follow the _recommendation for new packages with multiple versions_
in pkgs/by-name/README.md

pkgs/tools/misc/graylog/6.1.nix

@@ -0,0 +1,10 @@
+{ callPackage, lib, ... }:
+let
+  buildGraylog = callPackage ./graylog.nix { };
+in
+buildGraylog {
+  version = "6.1.8";
+  hash = "sha256-omyV4BSY9SWDFyLcQCr0+LcjRecw9C1HtvsnCJrZX1U=";
+  maintainers = with lib.maintainers; [ bbenno ];
+  license = lib.licenses.sspl;
+}

pkgs/top-level/all-packages.nix

@@ -3477,6 +3477,13 @@ with pkgs;
 
   graylog-6_0 = callPackage ../tools/misc/graylog/6.0.nix { };
 
+  inherit
+    ({
+      graylog-6_1 = callPackage ../tools/misc/graylog/6.1.nix { };
+    })
+    graylog-6_1
+    ;
+
   graylogPlugins = recurseIntoAttrs (
     callPackage ../tools/misc/graylog/plugins.nix { graylogPackage = graylog-6_0; }
   );