We test compilation with default features enabled and all features enabled, but not with combinations beyond that. See here for an example of a compilation failure related to feature flag combination that we didn't catch in CI: https://github.com/mongodb/mongo-rust-driver/issues/1291#event-16059818065. We should test more feature flag combinations - cargo-hack might be useful for this.

Edit - updated ticket description to test with no default features enabled rather than combinations.