Credits: every AtlasAccount has a credit balance. When it hits 0 the account is suspended
and all API calls return 401 until topped up. Credit top-ups are handled via billing/the
dashboard (not the public API).
Instance limit: a service key may carry a maxInstances cap. Creating beyond it returns
403 Instance limit reached.
Rate limits: a key can be configured with rateLimitPerMinute / rateLimitPerDay. Set
these when you create or update a key.
IP allowlist: a key can optionally restrict the source IPs allowed to use it
(allowedIpAddresses).