nixos: services: nextcloud: add collabora

This needs to be configured through the "Nextcloud Office" app,
specifically the WOPI setting is important for security (I put both the
external IP, as well as `::1` and `127.0.0.1`).

modules/nixos/services/nextcloud/default.nix

@@ -4,6 +4,10 @@ let
   cfg = config.my.services.nextcloud;
 in
 {
+  imports = [
+    ./collabora.nix
+  ];
+
   options.my.services.nextcloud = with lib; {
     enable = mkEnableOption "Nextcloud";
     maxSize = mkOption {