Context

On non-primaries, verify insert oplog entries: after applying the insert, compare h and the hashed o.

On a mismatch, fassert with a stack crash until we have different modes for handling a mismatch.

Runs only on non-primaries (OplogApplication::Mode::kSecondary), with the feature flag on, for supported collections. We may want to add a helper for checking these conditions.

Acceptance criteria

• After applying an insert on a non-primary we compare the h value and the hashed o field.
• On mismatch, fassert and crash.
• Skipped on the primary, when the feature flag is off, on unsupported collections, and when h is absent.
• No update/delete handling (done in SERVER-128585 and SERVER-128533 respectively)
• Unit-test!
  • Round-trip / happy path: The recomputed h and size match the primary's h and no mismatch is reported.
  • Mismatch detected: when h diverges, the comparison reports a mismatch.
  • Without the feature flag or without h, we don't perform the check.
  • Non-steady-state modes (initial sync, recovering) neither generate nor compare h.
  • Unsupported collections are skipped.
  • Any helper functions that we use that can be unit tested are also unit-tested.