Fix everything.

system/services/server/mysql/default.nix

@@ -0,0 +1,23 @@
+{ config, lib, pkgs, ... }:
+{
+  config = lib.mkIf config.system.server.enable {
+    services.mysql = {
+      enable = true;
+      package = pkgs.mariadb;
+      ensureDatabases = [
+        "minecraft"
+      ];
+      ensureUsers = [
+        {
+          name = "minecraft";
+          ensurePermissions = {
+            "minecraft.*" = "ALL PRIVILEGES";
+          };
+        }
+      ];
+    };
+    environment.persistence."/persist".directories = [
+      "/var/lib/mysql"
+    ];
+  };
+}