Generating multiple swagger documents is not supported

[maurei]

Exposing multiple swagger documents as described here fails. The problem is that our custom ISchemaGenerator is registered as a singleton, causing the same ISchemaRepositoryAccessor to be reused for different documents.

The fix is to register our ISchemaGenerator as transient, probably.

Along the way, we should consider to not deviate from the lifetimes used in Swashbuckle for other similar services. We're going with singleton most of the time, which can lead to unexpected problems like it did here.