users: Add SSH key

modules/users/alexander.nix

@@ -47,6 +47,11 @@
             hostname = "codeberg.org";
             identityFile = "~/.ssh/codeberg_papatutuwawa";
           };
+          "collaborating.tuhh.de" = {
+            user = "git";
+            hostname = "collaborating.tuhh.de";
+            identityFile = "~/.ssh/gitlab_tuhh";
+          };
         };
       };