Bug 27593: Consistent behavior for club holds route

This patch:
- Fixes a malformed response when biblio_id is invalid
- Fixes the return status (400 => 404) when biblio_id is invalid
- Adapts the error strings to be consistent with the Cities.pm file

To test:
1. Apply the regression tests patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/api/v1/clubs_holds.t
=> FAIL: Tests fail
3. Apply this patch
4. Repeat 2
=> SUCCESS: Tests pass!
5. Sign off :-D

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

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

Koha/REST/V1/Clubs/Holds.pm

@@ -81,7 +81,7 @@ sub add {
             unless ($item) {
                 return $c->render(
                     status  => 404,
-                    openapi => { error => "item_id not found." }
+                    openapi => { error => "Item not found" }
                 );
             }
             else {
@@ -100,8 +100,8 @@ sub add {
 
         unless ($biblio) {
             return $c->render(
-                status  => 400,
-                openapi => "Biblio not found."
+                status  => 404,
+                openapi => { error => "Biblio not found" }
             );
         }