loopback/common/models/role.json

{
  "name": "Role",
  "properties": {

    "id": {
      "type": "string",
      "id": true,
      "generated": true
    },
    "name": {
      "type": "string",
      "required": true
    },
    "description": "string",
    "created": {
      "type":"date",
      "defaultFn": "now"
    },
    "modified": {
      "type":"date",
      "defaultFn": "now"
    }
  },
  "relations": {
    "principals": {
      "type": "hasMany",
      "model": "RoleMapping",
      "foreignKey": "roleId"
    }
  }
}