Resolve query parameters to models

Resolve query parameters to the appropriate model instances. For example, after the implementation, a route like: 
```js
router.get("/{userId}", async (req, res) => {
    const user = await User.findByPk(req.params.userId);

    return user;
});
```

Should be written to the following and achieve the same result: 
```js
router.get("/{user}", (req, res) => {
    return user;
});
```