title: How to use Loopback ACL modify permissions on the user role
body: <p>I am trying to understand the loopback acl but failed, if I can use loopback acl control role authorization, what should I do?</p>
  
  <p>When I get request</p>
  
  <pre><code>GET http://localhost:1337/api/Employees 401 (Unauthorized)
  {
    "error": {
      "name": "Error",
      "status": 401,
      "message": "Authorization Required",
      "statusCode": 401,
      "stack": "Error: Authorization Required
    }
  }
  </code></pre>
  
  <p>Here is an employee. The JSON configuration </p>
  
  <pre><code>{
    "name": "Employee",
    "base": "User",
    "properties": {
      "nickname": {
        "type": "string"
      }
    },
    "validations": [],
    "relations": {},
    "acls": [
      {
        "principalType": "ROLE",
        "principalId": "admin",
        "permission": "ALLOW",
        "accessType": "READ"
      }
    ],
    "methods": []
  }
  </code></pre>
  
  <p>The following code is to add an employee</p>
  
  <pre><code>{
    "nickname": "",
    "realm": "",
    "username": "",
    "credentials": "object",
    "challenges": "object",
    "email": "",
    "emailVerified": false,
    "verificationToken": "",
    "status": "",
    "created": "",
    "lastUpdated": "",
    "id": 0
  }
  </code></pre>
  
  <p>I don't know the inside of the loopback acls. How do I go to change To achieve access control effect?</p>