Consider moving to OpenAPI 3.1.x

[provokateurin]

In the latest version we can make use of the const keyword for single value enums and it should also be possible to solve

openapi-extractor/src/OpenApiType.php

Line 77 in 63bbc54

Logger::warning($this->context, 'Complex types can not be part of query or URL parameters. Falling back to string due to undefined serialization!');

.
https://www.npmjs.com/package/openapi-typescript already has 3.1 support, so it should be fine for all uses in the Nextcloud frontend itself.

[provokateurin]

Also the nullable keyword is no longer a thing because proper JSON schema is supported, so we'd avoid some awkward problems like #261.