Split xeon specific configuration from base

To accomodate the raccoon knights workstation, some of the configuration
pulled by m/common/main.nix has to be removed. To solve it, the xeon
specific parts are placed into m/common/xeon.nix and only the common
configuration is at m/common/base.nix.

Reviewed-by: Aleix Roca Nonell <aleix.rocanonell@bsc.es>

m/common/base/ssh.nix

@@ -0,0 +1,22 @@
+{ lib, ... }:
+
+let
+  keys = import ../../../keys.nix;
+  hostsKeys = lib.mapAttrs (name: value: { publicKey = value; }) keys.hosts;
+in
+{
+  # Enable the OpenSSH daemon.
+  services.openssh.enable = true;
+
+  # Connect to intranet git hosts via proxy
+  programs.ssh.extraConfig = ''
+    Host bscpm02.bsc.es bscpm03.bsc.es gitlab-internal.bsc.es alya.gitlab.bsc.es
+      User git
+      ProxyCommand nc -X connect -x localhost:23080 %h %p
+  '';
+
+  programs.ssh.knownHosts = hostsKeys // {
+    "gitlab-internal.bsc.es".publicKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIF9arsAOSRB06hdy71oTvJHG2Mg8zfebADxpvc37lZo3";
+    "bscpm03.bsc.es".publicKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIM2NuSUPsEhqz1j5b4Gqd+MWFnRqyqY57+xMvBUqHYUS";
+  };
+}