nixos: create 'modules/nixos' folder

Let's consolidate all modules under one path, so that NixOS,
home-manager, and nix-darwin (if I ever end up using it down the line)
would go under the same folder.

modules/nixos/services/nextcloud/default.nix

@@ -0,0 +1,86 @@
+# A self-hosted cloud.
+{ config, lib, pkgs, ... }:
+let
+  cfg = config.my.services.nextcloud;
+in
+{
+  options.my.services.nextcloud = with lib; {
+    enable = mkEnableOption "Nextcloud";
+    maxSize = mkOption {
+      type = types.str;
+      default = "512M";
+      example = "1G";
+      description = "Maximum file upload size";
+    };
+    admin = mkOption {
+      type = types.str;
+      default = "Ambroisie";
+      example = "admin";
+      description = "Name of the admin user";
+    };
+    passwordFile = mkOption {
+      type = types.str;
+      example = "/var/lib/nextcloud/password.txt";
+      description = ''
+        Path to a file containing the admin's password, must be readable by
+        'nextcloud' user.
+      '';
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    services.nextcloud = {
+      enable = true;
+      package = pkgs.nextcloud27;
+      hostName = "nextcloud.${config.networking.domain}";
+      home = "/var/lib/nextcloud";
+      maxUploadSize = cfg.maxSize;
+      configureRedis = true;
+      config = {
+        adminuser = cfg.admin;
+        adminpassFile = cfg.passwordFile;
+        dbtype = "pgsql";
+        dbhost = "/run/postgresql";
+        overwriteProtocol = "https"; # Nginx only allows SSL
+      };
+
+      notify_push = {
+        enable = true;
+        # Allow using the push service without hard-coding my IP in the configuration
+        bendDomainToLocalhost = true;
+      };
+    };
+
+    services.postgresql = {
+      enable = true;
+      ensureDatabases = [ "nextcloud" ];
+      ensureUsers = [
+        {
+          name = "nextcloud";
+          ensurePermissions."DATABASE nextcloud" = "ALL PRIVILEGES";
+        }
+      ];
+    };
+
+    systemd.services."nextcloud-setup" = {
+      requires = [ "postgresql.service" ];
+      after = [ "postgresql.service" ];
+    };
+
+    # The service above configures the domain, no need for my wrapper
+    services.nginx.virtualHosts."nextcloud.${config.networking.domain}" = {
+      forceSSL = true;
+      useACMEHost = config.networking.domain;
+    };
+
+    my.services.backup = {
+      paths = [
+        config.services.nextcloud.home
+      ];
+      exclude = [
+        # image previews can take up a lot of space
+        "${config.services.nextcloud.home}/data/appdata_*/preview"
+      ];
+    };
+  };
+}