Most importantly we don't require to share the code from gitbhub.
Github: Reads permissions repository, issues, teams, pull requests. Write: Pull Requests (so that we can write the conversations that happen in slack)
Slack: read and write Members, channels and private message to the bot
Unfortunately, Slack does not have that level of granularity yet, so the permissions are given to all public channels. But we only interact with Slack saving the ID of the specific channel we create, we do not store any information from other channels.