Switch from swagger-codegen to kiota

Other Granta MI consumers of OpenAPI specs use [kiota](https://github.com/microsoft/kiota) instead of swagger-codegen. kiota generates nicer Python and seems to be well supported, but there are currently issues that are blocking us making the switch:

* https://github.com/microsoft/kiota/issues/4868
* Lack of support for Windows auth

Start by reviewing the linked Kiota issue and investigating the stated Windows authentication limitation. The issue provides no repository files, tests, or entry points; it is complete only when the blockers are resolved and OpenAPI client generation has been switched from swagger-codegen to Kiota.

Written by the indexing model from the issue text.