Bug 41889: Update API to allow for null patron_id to be returned when listing checkouts

If a patron is deleted and there's a checkout associated with them, an api call to {url}/api/v1/checkouts?checked_in=true
will result in an error. This patch updates the api to allow for a null value to be returned for patron_id

To test:
Before applying the patch:

1. In Administration->System preference enable the RESTBasicAuth system preference.
2. Checkout an item to a patron (I used item barcode: 39999000000252 and patron barcode 23529000121682)
3. Check the item back in
4. In your brower go to {sandbox/ktdurl}/api/v1/checkouts?checked_in=1
5. Observe there is a patron ID in the JSON response
6. Delete the patron
7. Repeat step 4
8. Observe an error because a "null" value was returned
9. Apply patch
   Sandbox:
       In sandbox management Actions->Apply patches
       Once complete Actions->Build CSS and JS
       Actions->Restart services
   KTD:
       ktd --shell
       git bz apply 41889
       yarn build
       restart_all

10. Repeat step 4
11. Observe the checkout loads, but now has a null patron id.
12. Sign off
On KTD can also run the script: qa
to run tests.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Tomás Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Pedro Amorim <pedro.amorim@openfifth.co.uk>

api/v1/swagger/definitions/checkout.yaml

@@ -5,7 +5,9 @@ properties:
     type: integer
     description: internally assigned checkout identifier
   patron_id:
-    type: integer
+    type:
+      - integer
+      - "null"
     description: Internal patron identifier
   item_id:
     type:

t/db_dependent/api/v1/checkouts.t

@@ -18,7 +18,7 @@
 use Modern::Perl;
 
 use Test::NoWarnings;
-use Test::More tests => 112;
+use Test::More tests => 113;
 use Test::MockModule;
 use Test::Mojo;
 use t::lib::Mocks;
@@ -33,6 +33,8 @@ use Koha::Database;
 use Koha::DateUtils qw( dt_from_string output_pref );
 use Koha::Token;
 
+use JSON qw(encode_json );
+
 my $schema  = Koha::Database->schema;
 my $builder = t::lib::TestBuilder->new;
 
@@ -759,3 +761,58 @@ subtest 'renew with fine override (x-koha-override: debt_limit)' => sub {
 
     $schema->storage->txn_rollback;
 };
+
+subtest 'list checkouts that have been checked in and the patron has been deleted' => sub {
+    plan tests => 6;
+
+    $schema->storage->txn_begin;
+
+    # Create a librarian with circulate permission
+    my $librarian = $builder->build_object(
+        {
+            class => 'Koha::Patrons',
+            value => { flags => 2 }     # Superlibrarian
+        }
+    );
+    my $password = 'thePassword123';
+    $librarian->set_password( { password => $password, skip_validation => 1 } );
+    my $userid = $librarian->userid;
+
+    # Create a regular patron
+    my $patron = $builder->build_object(
+        {
+            class => 'Koha::Patrons',
+            value => { flags => 0 }
+        }
+    );
+    my $patron_id = $patron->borrowernumber;
+
+    my $old_checkout = $builder->build_object(
+        {
+            class => 'Koha::Old::Checkouts',
+            value => { borrowernumber => $patron_id }
+        }
+    );
+    my $old_checkout_id = encode_json( { checkout_id => $old_checkout->id } );
+
+    # Test 1: Checkout should be returned
+    $t->get_ok("//$userid:$password@/api/v1/checkouts?checked_in=1&q=$old_checkout_id")
+        ->status_is(200)
+        ->json_is( '/0/patron_id' => $patron_id );
+
+    my $old_checkout_2 = $builder->build_object(
+        {
+            class => 'Koha::Old::Checkouts',
+            value => { borrowernumber => undef }
+        }
+    );
+    my $old_checkout_2_id = encode_json( { checkout_id => $old_checkout_2->id } );
+
+    # Test 2: Checkout should be returned with null patron_id
+
+    $t->get_ok("//$userid:$password@/api/v1/checkouts?checked_in=1&q=$old_checkout_2_id")
+        ->status_is(200)
+        ->json_is( '/0/patron_id' => undef );
+
+    $schema->storage->txn_rollback;
+};