Proposes a non-human credential type — service_accounts +
service_account_keys, instance- or team-scoped, distinct from both
user API keys (always tied to a human's full rights) and integration
keys (narrow, one-way webhook auth only). Directly unblocks
terdut-operator's DESIGN.md §6, whose bootstrap/rotation plan doesn't
work against /api/bootstrap's actual single-shot-per-install behavior.
Design note only, no implementation yet.
Niklas Ye