In some deployments there are existing mechanism for handling secrets which would be preferred to having them in the mongo db.
This also unifies 2 code paths for configuring PagerDuty.
Testing:
- Automated tests pass
- Original flow of storing these secrets in mongo works
- Using env vars instead works (although the admin will incorrectly show an error for the slack token and I had to make any dummy edit to cause it to save the bot settings)