Application-owned callback reporting the driver's connection-pool
counters (M90b). The application reads its own driver's documented pool
API — the configured Drizzle identity is opaque to this package — and
the adapter publishes the returned DatabasePoolCapacity
snapshot to the database health indicator through an internal seam.
Omitted, the indicator carries no capacity fields. No threshold is applied: saturation is data, not policy.
() => DatabasePoolCapacity