LinkedIn Auth sample does not generalize

### How to reproduce these conditions
**Steps to set up and reproduce**
- Use the LinkedIn auth sample, make sure it works
- Change it to work with Bing Ads instead, changing only the endpoints and id/secret

**Sample data pasted or attached as JSON (not an image)**
```
{ name: 'Error',
status: 401,
message: 'Unauthorized',
context:
{ error: 'invalid_client',
error_description: 'The provided value for the \'client_secret\' parameter is not valid.' } }
```

### Expected behavior
The token request should work the same because OAuth2 is a standard

### Actual behavior
It doesn't work the same and fails for one system while working for the other.