MDL-78572 badges: Improve debugging

Display more information, like the status error, when the badge can't
be sent to the backpack.

Backport from MDL-77086

badges/classes/backpack_api2p1.php

@@ -272,8 +272,19 @@ public function put_assertions($hash) {
             $msg['status'] = \core\output\notification::NOTIFY_SUCCESS;
             $msg['message'] = get_string('addedtobackpack', 'badges');
         } else {
+            $statuserror = $response->status->error;
+            if (is_array($statuserror)) {
+                // Although the specification defines that status error is a string, some providers, like Badgr, are wrongly
+                // returning an array. It has been reported, but adding this extra check doesn't hurt, just in case.
+                $statuserror = implode($statuserror);
+            }
+            $data = [
+                'badgename' => $data['assertion']['badge']['name'],
+                'error' => $statuserror,
+            ];
+
             $msg['status'] = \core\output\notification::NOTIFY_ERROR;
-            $msg['message'] = get_string('backpackexporterror', 'badges', $data['assertion']['badge']['name']);
+            $msg['message'] = get_string('backpackexporterrorwithinfo', 'badges', $data);
         }
         return $msg;
     }

lang/en/badges.php

@@ -130,6 +130,7 @@
 $string['backpackemailverifysuccess'] = 'Thanks for verifying your email address. You are now connected to your backpack.';
 $string['backpackemailverifytokenmismatch'] = 'The token in the link you clicked does not match the stored token. Make sure you clicked the link in most recent email you received.';
 $string['backpackexporterror'] = 'Can\'t export the badge to backpack';
+$string['backpackexporterrorwithinfo'] = 'Can\'t export the badge "{$a->badgename}" to backpack. Error: {$a->error}';
 $string['backpackimport'] = 'Badge import settings';
 $string['backpackimport_help'] = 'After the backpack connection is successfully established, badges from your backpack can be displayed on your badges page and your profile page.