Adds a new endpoint to the Users API controller allowing developers to retrieve a user based on one of three criteria:
- user_id
- email
- username
All parameters are optional and if more than one is specified, the search is performed against each criteria above in the order listed.
For example, if all three parameters are specified and a user_id match is found, that will be returned regardless of the email or username parameters. Similarly, if the user_id is not found...