Update the code generators

[queicherius]

WIP branch: https://github.com/devoxa/paddle-sdk/tree/fix-generators

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On hold

I have sent the issues below to the Paddle support, and this is on hold until they respond (and hopefully improve things).

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1. The documentation changed from JSON schemas to markdown

Parsing markdown tables & manually typed text is possible, but it makes it harder than it needs to be, and needs a bunch of random hacks to get around inconsistencies.

2. The documentation is incorrect in large parts

• generate-pay-link shows request.prices is a string. It should be an Array<string> | string
• list-users is missing response.quantity in the schema. It is shown in the example response and should be an integer?.
• list-users is showing response.next_payment as an object. It should be an object?.
• order-processing-completed shows a default for alert_id when it's actually for alert_name.

I'm sure there are plenty more examples - those are just the ones I found in the first few endpoints I looked at, not even checking against the API. Without trying it out, there is currently no way of knowing what the API expects or responds with.