feat(gaurds): use better smartguards to verify action authorization

ts/manager.auth/classes.user.ts

@@ -2,5 +2,23 @@ import * as plugins from '../plugins.js';
 
 @plugins.smartdata.managed()
 export class User extends plugins.smartdata.SmartDataDbDoc<User, User> {
-  
+  public static async findUserByUsernameAndPassword(usernameArg: string, passwordArg: string) {
+    return await User.getInstance({
+      data: {
+        username: usernameArg,
+        password: passwordArg,
+      }
+    });
+  }
+
+  // INSTANCE
+  @plugins.smartdata.unI()
+  public id: string;
+
+  @plugins.smartdata.svDb()
+  public data: {
+    role: 'admin' | 'user';
+    username: string;
+    password: string;
+  }
 }