Added features of CircuitBreaker, Retry, Logger, and documentation

Author: Surfoo

README.md

@@ -32,13 +32,9 @@ First, you must have your API key from Groundspeak, but access to the API are no
 
 You can find an example of implementation (with OAuth 2) in this repository: https://github.com/Surfoo/geocaching-api-demo
 
-## Usage Guide
+## Documentation
 
-See [`USAGE.md`](./USAGE.md) for detailed usage instructions, including:
-
-- Basic usage examples
-- Complete API method reference
-- HTTP logging configuration
+Start with [`docs/README.md`](./docs/README.md) for getting started, authentication, configuration, reliability patterns, and domain-by-domain API examples.
 
 ## HTTP Request/Response Logging
 

USAGE.md

@@ -0,0 +1,10 @@
+# Geocaching PHP SDK Documentation
+
+This folder collects the SDK documentation with examples for the Groundspeak Geocaching API. Each page focuses on a specific topic so you can jump straight to what you need.
+
+## Contents
+- [Getting Started](./getting-started.md) — install the package, create an SDK client, and make your first request.
+- [Authentication & Tokens](./authentication.md) — work with access tokens, wire OAuth, and enable automatic refresh.
+- [Configuration & HTTP Clients](./configuration.md) — understand runtime options, environments, and how to plug in custom PSR clients.
+- [Reliability & Observability](./reliability.md) — enable structured logging, retries, and circuit breaking for resilient calls.
+- [API Usage by Domain](./api-usage.md) — call the main API areas (geocaches, users, adventures, trackables, lists, status) with documented examples.