Bug 20212: Remove fix_query and assume ugliness

Bug 20212: Remove fix_query and assume ugliness

It seems better to do things in an ugly way but simple than complicated.
This patch removes the fix_query method that deals with ean and isbn and
explicitly tell that it's a trick that must not be reused somewhere
else.
It should only be used by Koha internally and we should not advertised
it until it's ready.
This problem will have to be fixed properly when the GET /biblios route
will be implemented.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>