Bug 33227: Remove invalid spec and adjust the code accordingly

Bug 33227: Remove invalid spec and adjust the code accordingly

The spec contains a non-standard definition for the body param. Removing
it from the spec makes us need to handle the 'body' manually in the case
of JSON data.

This patch basically does that. It also changes the uses of
$c->validation, which are discouraged by the
Mojolicious::Plugin::OpenAPI dev/maintainer. I do it to highlight what
we must do in other places and the fact that there's no behavior change.

To test:
1. Apply this patch
2. Run:
   $ ktd --shell
  k$ prove t/db_dependent/api/v1/biblios.t \
           xt/api.t
=> SUCCESS: Tests pass!
3. Sign off :-D

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>