Create a Slack app. Click "Add features and functionality," and add the "Bots" feature.
Set up ngrok for development. Run ngrok http http://0.0.0.0:8080 to expose your local server to the internet.
Copy the URL ngrok gives you (it'll be something like http://abc123.ngrok.io).
Go back to your Slack app's settings and add the ngrok URL in the Slack app permissions page under "Redirect URIs" with /oauth at the end of it (so, in our example, http://abc123.ngrok.io/oauth)
If you're developing against the production version of Camille setup redis. Docker is an easy way to do this. If you have docker installed, run docker run --name redis -p 6379:6379 -d redis. Otherwise you can use MemoryStorage in place of redis.
Set the project's environment variables. Click the scheme dropdown, and hit "edit scheme."
Set the STORAGE_URL environment variable to the redis URL (redis://127.0.0.1:6379 by default)
Set CLIENT_ID and CLIENT_SECRET to the IDs that Slack shows on your App page. (Alternatively message @mergesort for some development credentials you can use for testing an integration.)
Set REDIRECT_URI to the redirect URL we set earlier ( http://abc123.ngrok.io/oauth, in our example)
Run the project
Visit http://0.0.0.0:8080/login and authorize the app.