The Slack integration will use the [Users.info](https://api.slack.com/methods/users.info) API to get the appropriate details for the Slack User.
Feel free to implement this solution using the language of your choice.
- Extensible User Data Model
- Extensible API Invocation Model
- Slack Integration using the above model
- Logical Integration Tests for your implementation
Note: For testing purposes you may want to spin up your own Slack Workspace and generate a web token. They are free and easy to setup, just go through Slack.com and create an account if you currently don't have one.
Creating a Slack Workspace
Generating a Slack Token