v2.2.0

• Support Guzzle 7 on current PHP while retaining Guzzle 6 for older runtimes.
• Correct the declared PHP floor to the existing dependency-required PHP 5.5 minimum and verify runtime installation there.
• Normalize Cachet base URLs so callers may omit the trailing slash.
• Allow callers to inject a Guzzle client or configure client options such as timeouts, proxies, middleware, and test handlers.
• Add passing PHP 5.5 runtime, PHP 7.4 behavior, and PHP 8.5 behavior validation.