Upgrade dependencies

[tommitchelmore]

Dependency Upgrades

This PR upgrades the major version of several dependencies

• mindplay/middleman - 3.x → 4.x - No breaking changes, required changing two instances of dispatch() to the PSR-compliant handle() (see the upgrade guide).
• laminas/laminas-diactoros - 2.x → 3.x - No breaking changes (see the upgrade guide).
• psr/container - 1.x → 2.x - No breaking changes
• psr/http-message - 1.x → 2.x - No breaking changes
• php-di/php-di - 6.x → 7.x - Required upstream by Lumberjack, no breaking changes (required a change to the container creation in tests - see upgrade guide).

Breaking Changes

• Now requires PHP 8.4 ⚠️
• When registering a route, you can no longer use first-class callables
  • SomeController::staticMethod(...) → SomeController::class, 'staticMethod']
  • This is because in PHP 8.1 Class::method creates a Callable which no longer reports it's name to is_callable (all it returns is 'Closure'). I'm not sure why this was working in PHP 8.1-3 but this is now in-line with Laravel's routing.

Note on testing

Two tests were modified regarding middleware dispatching. This is to reflect Middleman removing dispatch in favour of the PSR compatible handle method.