0.27.0

This release includes significant API changes. See UPGRADING.md
for migration guidance.

Breaking Changes

Lookup API

• lookup() now returns LookupResult instead of Option<T>. The new API
  enables lazy decoding - data is only deserialized when explicitly requested.
• lookup_prefix() has been removed. Use lookup(ip)?.network() instead.

Iteration API

• within() now requires a second WithinOptions parameter. Use
  Default::default() for the previous behavior.
• Within iterator now yields LookupResult instead of WithinItem<T>.

GeoIP2 Structs

• The names fields now use a Names struct instead of BTreeMap<&str, &str>.
  Access names directly via language fields (e.g., names.english).
• Nested struct fields (city, country, location, etc.) are now
  non-optional with Default, simplifying access patterns.
• Removed is_anonymous_proxy and is_satellite_provider from Traits.
  These fields are no longer present in MaxMind databases.

Error Types

• InvalidDatabase and Decoding variants now use structured fields instead
  of a single string. Pattern matching must be updated.
• New InvalidInput variant for user input errors (e.g., IPv6 lookup in
  IPv4-only database).

Memory Mapping

• Reader::open_mmap is now unsafe. The caller must ensure the database
  file is not modified or truncated while the Reader exists. This fixes a
  soundness issue. Reported by paolobarbolini. GitHub #86.

Added

• LookupResult type with lazy decoding support:
  • has_data() - Check if data exists for this IP
  • network() - Get the network containing the IP
  • offset() - Get data offset for caching/deduplication
  • decode() - Deserialize full record
  • decode_path() - Selectively decode specific fields by path
• PathElement enum and path! macro for navigating nested structures.
• WithinOptions to control network iteration behavior:
  • include_aliased_networks() - Include IPv4 via IPv6 aliases
  • include_networks_without_data() - Include networks without data records
  • skip_empty_values() - Skip empty maps/arrays
• networks() method for iterating over all networks in the database.
• verify() method for comprehensive database validation.
• Metadata::build_time() to convert build_epoch to SystemTime.
• PartialEq and Eq implementations for Metadata and WithinOptions.

Changed

• Error messages now include byte offsets when available.
• decode_path() errors include path context showing where navigation failed.
• Added recursion depth limit (512) matching libmaxminddb and Go reader.
• Serde deserializer improvements: size hints, is_human_readable() returns
  false, deserialize_ignored_any, and deserialize_enum support.
• MaxMindDbError is now #[non_exhaustive].