feat: secrets (#8070)

docs/usage/self-hosted-configuration.md

lib/config/__snapshots__/secrets.spec.ts.snap

lib/config/definitions.ts

lib/config/secrets.spec.ts

lib/config/secrets.ts

lib/config/types.ts

lib/constants/error-messages.ts

lib/logger/index.spec.ts

lib/logger/utils.ts

lib/workers/global/index.ts

lib/workers/repository/init/index.spec.ts

lib/workers/repository/init/index.ts