As an admin, I would like to see a list of all shortlinks that have been created by other users

From shortener-interview-base created by [kayakyakr](https://github.com/kayakyakr): kapost/shortener-interview-base#3  

## Acceptance Criteria

- New API method that returns a list of all shortlinks that have been created
- Display shortlinks in client side