Have your coding agent describe your Online integration

Describe this codebase’s QuickBooks Online integration so another team can build the same integration for QuickBooks Desktop. Write one Markdown document. Leave out API keys, tokens and customer data.

Cover:
1. Who we are: our company's name and website, what our product does, and who uses it, in a paragraph a non-developer could follow.
2. Our stack: language and version, web framework, the HTTP client library we use, the background job system, and how we receive webhooks.
3. Every QuickBooks Online entity it reads or writes (Customer, Invoice, Payment, Item…). For each: the direction, the model of ours it maps to, and the fields it sets or reads.
4. What starts each sync: a user action, an event in our app, a QuickBooks webhook or a schedule.
5. How it finds records already in QuickBooks (by Id, name, email or DocNumber), and what it does when it finds none or several.
6. The settings our users choose (income accounts, items, tax codes, classes) and where they’re kept.
7. What happens when QuickBooks refuses a request, and what our user sees.
8. Anything it relies on that only QuickBooks Online has.
9. Our data models, as JSON Schema, in one ```json block at the end: `$defs` with an entry per model in item 3, keyed by its class name, with every field it reads or writes for QuickBooks (its type, whether it can be null, its `enum` when it has a fixed set of values) and each association as a `$ref` to the other model, or an array of them for a has-many. Generate it from the schema file or the models, don’t write it by hand, and describe the shape only: no real records, no `examples` or `default` values. Leave it out if the models can’t be read.

Works with any agent that can read your repository. It asks how the integration behaves, never for keys, passwords or customer data.