Create comprehensive user documentation for the backend system of the oslo.service project. The documentation should focus exclusively on the backend functionality, including:

• An overview of the backend architecture and components.
• Detailed explanations of:
  • How to initialize the backend.
  • How to access and use backend components.
  • How to test and reset the backend (for testing purposes only).
  • Guidelines for customization and extensibility (e.g., adding new backends).
• A complete usage example demonstrating backend initialization and component access.
•  Relevant references for further reading.