sqls: add module

sqls is a SQL language server written in Go.
See: https://github.com/lighttiger2505/sqls

modules/programs/sqls.nix

@@ -0,0 +1,47 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.programs.sqls;
+
+  yamlFormat = pkgs.formats.yaml { };
+
+in {
+  meta.maintainers = [ maintainers.marsam ];
+
+  options.programs.sqls = {
+    enable = mkEnableOption "sqls, a SQL language server written in Go";
+
+    settings = mkOption {
+      type = yamlFormat.type;
+      default = { };
+      example = literalExpression ''
+        {
+           lowercaseKeywords = true;
+           connections = [
+             {
+               driver = "mysql";
+               dataSourceName = "root:root@tcp(127.0.0.1:13306)/world";
+             }
+           ];
+        }
+      '';
+      description = ''
+        Configuration written to
+        <filename>$XDG_CONFIG_HOME/sqls/config.yml</filename>. See
+        <link xlink:href="https://github.com/lighttiger2505/sqls#db-configuration"/>
+        for supported values.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    home.packages = [ pkgs.sqls ];
+
+    xdg.configFile."sqls/config.yml" = mkIf (cfg.settings != { }) {
+      source = yamlFormat.generate "sqls-config" cfg.settings;
+    };
+  };
+}