MDL-80836 auth_lti: take user through login instead of sesspiggyback

Browsers are phasing out 3rd party cookies. Those which can be set are
partitioned to the top level embedding site, so piggybacking is
prevented. This will break the account linking process. This fix swaps
the piggyback for a login round trip, as originally intended, which
resolves the issue.

auth/lti/classes/output/renderer.php

@@ -33,33 +33,32 @@ class renderer extends \plugin_renderer_base {
      * @return string the html.
      */
     public function render_account_binding_options_page(int $provisioningmode): string {
+
         $formaction = new \moodle_url('/auth/lti/login.php');
         $notification = new notification(get_string('firstlaunchnotice', 'auth_lti'), \core\notification::INFO, false);
-        $noauthnotice = new notification(get_string('firstlaunchnoauthnotice', 'auth_lti', get_docs_url('Publish_as_LTI_tool')),
-            \core\notification::WARNING, false);
         $cancreateaccounts = !get_config('moodle', 'authpreventaccountcreation');
         if ($provisioningmode == \auth_plugin_lti::PROVISIONING_MODE_PROMPT_EXISTING_ONLY) {
             $cancreateaccounts = false;
         }
 
-        $accountinfo = ['isloggedin' => isloggedin()];
+        $accountinfo = [];
         if (isloggedin()) {
             global $USER;
-            $accountinfo = array_merge($accountinfo, [
+            $accountinfo = [
                 'firstname' => $USER->firstname,
                 'lastname' => $USER->lastname,
                 'email' => $USER->email,
                 'picturehtml' => $this->output->user_picture($USER,  ['size' => 35, 'class' => 'round']),
-            ]);
+            ];
         }
 
         $context = [
+            'isloggedin' => isloggedin(),
             'info' => $notification->export_for_template($this),
             'formaction' => $formaction->out(),
             'sesskey' => sesskey(),
             'accountinfo' => $accountinfo,
             'cancreateaccounts' => $cancreateaccounts,
-            'noauthnotice' => $noauthnotice->export_for_template($this)
         ];
         return parent::render_from_template('auth_lti/local/ltiadvantage/login', $context);
     }

auth/lti/lang/en/auth_lti.php

@@ -35,7 +35,7 @@ $string['firstlaunchnoauthnotice'] = 'To link your existing account you must be
 $string['getstartedwithnewaccount'] = 'Get started with a new account';
 $string['haveexistingaccount'] = 'I have an existing account';
 $string['linkthisaccount'] = 'Link this account';
-$string['mustbeloggedin'] = 'You need to be logged in to your existing account';
+$string['mustbeloggedin'] = 'Sign in to link your existing account';
 $string['pluginname'] = 'LTI';
 $string['privacy:metadata:auth_lti'] = 'LTI authentication';
 $string['privacy:metadata:auth_lti:authsubsystem'] = 'This plugin is connected to the authentication subsystem.';

auth/lti/templates/local/ltiadvantage/login.mustache

@@ -32,7 +32,6 @@
     * info - a notification describing the first launch options
     * cancreateaccounts - whether or not the user is allowed to create auth_lti accounts
     * accountinfo - information about the user, importantly whether they are logged in or not.
-    * noauthnotice - a notification telling the user they must be authenticated to link accounts. Only relevant when not logged in.
 
     Example context (json):
     {
@@ -46,19 +45,12 @@
             "issuccess": true
         },
         "cancreateaccounts": true,
+        "isloggedin": true,
         "accountinfo": {
-            "isloggedin": true,
             "firstname": "John",
             "lastname": "Smith",
             "email": "john@example.com",
             "picturehtml": "<img src=\"http://site.example.com/pluginfile.php/5/user/icon/boost/f2?rev=99\" class=\"round\" alt=\"\" width=\"35\" height=\"35\">"
-        },
-        "noauthnotice": {
-            "message": "To link your existing account you must be logged in to the site...",
-            "extraclasses": "",
-            "announce": false,
-            "closebutton": false,
-            "iswarning": true
         }
     }
 }}
@@ -79,8 +71,8 @@
                         <div class="card-body text-center d-flex flex-column">
                             <i class="fa fa-user-circle-o fa-2x link"></i>
                             <h4 class="card-title">{{#str}} useexistingaccount, auth_lti {{/str}}</h4>
-                            {{#accountinfo}}
                                 {{#isloggedin}}
+                                    {{#accountinfo}}
                                     <p class="card-text mt-2">
                                         <span class="text-muted">
                                             {{#str}} currentlyloggedinas, auth_lti {{/str}}
@@ -90,14 +82,12 @@
                                         {{firstname}} {{lastname}} ({{email}})
                                     </p>
                                     <input type="submit" class="btn btn-primary mt-auto" name="existing_account" value="{{#str}} linkthisaccount, auth_lti {{/str}}">
+                                    {{/accountinfo}}
                                 {{/isloggedin}}
                                 {{^isloggedin}}
                                     <p class="card-text text-muted">{{#str}} mustbeloggedin, auth_lti {{/str}}</p>
-                                    {{#noauthnotice}}
+                                    <input type="submit" class="btn btn-primary mt-auto" name="existing_account" value="{{#str}} login, moodle {{/str}}">
-                                        {{> core/notification}}
-                                    {{/noauthnotice}}
                                 {{/isloggedin}}
-                            {{/accountinfo}}
                         </div>
                     </div>
                 </div>