I am a product manager who doesn't understand technology. I want to thoroughly organize the business logic using Mermaid diagrams. Please help me analyze what valuable points can be extracted here. Help me write several detailed explanation documents, placed in docs/explain/*.md. The documents must extensively use Mermaid syntax to visualize the logic. The more detailed, the better, the more detailed, the better, the more detailed, the better, so that even if I don't understand technology, I can clearly see the direction of the business logic. Thank you for your hard work!