Better to leave the version in there because Swagger Editor doesn't
like it without. Also, change the example page parameter for POSTing
to /items and /collections, as it doesn't make sense to start on a
later page if we have less items than our limit.
This includes a Swagger UI with an OpenAPI 3.0 JSON schema for easy
interactive demonstration and testing of the API. The JSON schema
was created with the standalone swagger-editor. Includes tests to
make sure that the /swagger and /docs/openapi.json paths are acce-
ssible.