V2: Architectural rewrite

[Nielsvanpach]

Summary

Major version rewrite focused on type safety, performance, and a cleaner architecture. Breaking changes are documented in UPGRADING.md.

For users

• Improved supports for types of holidays: national, regional, observed, religious or bank
• New API methods
• get() and getInRange() now return Holiday[] value objects instead of plain arrays
• Holidays::for() accepts a region parameter directly
• Most countries now support any year (no more global 1970–2037 limit)
• Requires PHP 8.4+

For contributors

• All dates are CarbonImmutable throughout — no more implicit string parsing
• Translation logic moved into the Country base class
• HasRegions interface standardizes regional holidays
• HasObservedHolidays trait replaces Observable with clearer method signatures
• ResolvesCalendarDates trait deduplicates calendar logic
• CountryRegistry replaces filesystem scanning

Performance

• Country discovery via static registry instead of glob()
• No per-holiday string-to-date parsing overhead

Links

• UPGRADING.md — full migration guide
• README.md — rewritten with comprehensive "Adding a new country" guide