Authenticates a User using a username and password, and returns its unique identifier on success.
| Get | api/users/authenticate | 
Resource Path: /sites/{company-id}/api/users/authenticate
Uri: https://secure.ontime360.com/sites/{company-id}/api/users/authenticate
| Name | Description | Data Type | 
|---|---|---|
| userName | The User's username as a plain-text String. | string | 
| password | The User's password as a plain-text String. | string | 
The response body is of type string.
On success, returns the User's unique identifier as a Guid. Returns null if the username or password does not belong to any existing User.| Fault | Description | 
|---|---|
| 400 | Request was improperly formatted, contained invalid data, or contained incorrect values. See response body for more information. | 
| 401 | Authorization key is invalid or no longer exists. | 
| 403 | Authorization key does not have permission to perform this action, or does not have permission to access the requested data. See response body for more information. |