Remove the skip on the test test_no_params_sent, since the version 0.19.1 of
pyramid-openapi3 fix the problem.

See https://github.com/Pylons/pyramid_openapi3/issues/260 and
https://github.com/Pylons/pyramid_openapi3/pull/259.

This is enforced by pyramid-openapi3.

Also upgrade from openapi version 3.0.3 to 3.1.0

- nullables are replaced by the "null" type.
- application/octet-stream content schema don't require specifying a schema

Mutating the original requests can be dangerous and have unwanted side effects.

For example, it can prevent the signedrequest cube from checking authenticity
of a request as it compares the signature received in the request's header with the
signature of the body.

Which will allow adding metadata to resultsets.

disabled by default, marked as experimental

OpenAPI spec now always shows the login/logout routes