roles: implement dbserver mariadb and postgresql roles

roles/dbserver-mariadb.nix

@@ -0,0 +1,41 @@
+# Module: roles/dbserver-mariadb
+# Enables a database server running MariaDB
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.dbserver-mariadb;
+  defaultDBPackage = mariadb;
+  defaultPyMySQLPackage = python313Packages.pymysql;
+in {
+  options.dbserver-mariadb = {
+    enable = mkEnableOption "Enables dbserver-mariadb role";
+
+    dbPackage = mkOption {
+      type = types.package;
+      default = defaultDBPackage;
+      description = "Package to use for the database server";
+      example = mariadb;
+    };
+
+    ansibleLibPackage = mkOption {
+      type = types.package;
+      default = defaultPyMySQLPackage;
+      description = "Python library to use for Ansible interfacing";
+      example = python313Packages.pymysql;
+    };
+  };
+
+  config = mkIf config.dbserver-mariadb.enable {
+    environment.systemPackages = with pkgs; [
+      cfg.dbPackage
+      cfg.ansibleLibPackage
+    ];
+
+    services.mysql = {
+      enable = true;
+      package = cfg.dbPackage;
+    };
+  };
+}

roles/dbserver-postgresql.nix

@@ -0,0 +1,40 @@
+# Module: roles/dbserver-postgresql
+# Enables a database server running PostgreSQL
+
+with lib;
+
+let
+  cfg = config.dbserver-postgresql;
+  defaultPostgresPackage = postgresql;
+  defaultPsycopg2Package = python313Packages.psycopg2;
+in {
+  options.dbserver-postgresql = {
+    enable = mkEnableOption "Enables dbserver-postgresql role";
+
+    dbPackage = mkOption {
+      type = types.package;
+      default = defaultPostgresPackage;
+      description = "Package to use for the database server";
+      example = postgresql;
+    };
+
+    ansibleLibPackage = mkOption {
+      type = types.package;
+      default = defaultPsycopg2Package;
+      description = "Python library to use for Ansible interfacing";
+      example = python313Packages.psycopg2;
+    };
+  };
+
+  config = mkIf config.dbserver-mariadb.enable {
+    environment.systemPackages = with pkgs; [
+      cfg.dbPackage
+      cfg.ansibleLibPackage
+    ];
+
+    services.postgresql = {
+      enable = true;
+      package = cfg.dbPackage;
+    };
+  };
+}