MDL-79725 libraries: fix auth URL generation in lti1p3 library

lib/lti1p3/readme_moodle.txt

@@ -2,6 +2,8 @@ LTI 1.3 Tool Library import instructions
 
 This library is a patched for use in Moodle - it requires the following changes be applied on top of the packback upstream base:
 1. Removal of phpseclib dependency (replaces a single call with openssl equivalent)
+2. Apply the fix from https://github.com/packbackbooks/lti-1-3-php-library/pull/107. If this is already merged upstream, please
+remove this line.
 
 To upgrade to a new version of this library:
 1. Clone the latest version of the upstream library from github:

lib/lti1p3/src/LtiOidcLogin.php

@@ -90,7 +90,12 @@ class LtiOidcLogin
             $auth_params['lti_message_hint'] = $request['lti_message_hint'];
         }
 
-        $auth_login_return_url = $registration->getAuthLoginUrl().'?'.http_build_query($auth_params, '', '&');
+        if (parse_url($registration->getAuthLoginUrl(), PHP_URL_QUERY)) {
+            $separator = '&';
+        } else {
+            $separator = '?';
+        }
+        $auth_login_return_url = $registration->getAuthLoginUrl().$separator.http_build_query($auth_params, '', '&');
 
         // Return auth redirect.
         return new Redirect($auth_login_return_url, http_build_query($request, '', '&'));