A new, required configuration value "DATABASE_SECRET_KEY" will be introduced with the following PR: https://github.com/quay/quay/pull/3623

This configuration value should be documented before a release is made including this change-set.

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Documentation needed:

For existing installations only:

1. Open `config.yaml`
2. Generate some random data using `openssl rand -hex 48`
3. Add a new field `DATABASE_SECRET_KEY: "therandomstringhere"`
4. Make sure the same value is on all nodes