MDL-64148 oauth2: Make email greetings consistent

Some email body strings use first names as greetings,
some use full names, and some do not.

Using the first name for greeting makes it consistent and
a bit more "personal".

auth/oauth2/classes/api.php

@@ -176,7 +176,10 @@ class api {
         $user = get_complete_user_data('id', $userid);
 
         $data = new stdClass();
-        $data->fullname = fullname($user);
+        $placeholders = \core_user::get_name_placeholders($user);
+        foreach ($placeholders as $field => $value) {
+            $data->{$field} = $value;
+        }
         $data->sitename  = format_string($site->fullname);
         $data->admin     = generate_email_signoff();
         $data->issuername = format_string($issuer->get('name'));
@@ -319,7 +322,10 @@ class api {
         $user = get_complete_user_data('id', $user->id);
 
         $data = new stdClass();
-        $data->fullname = fullname($user);
+        $placeholders = \core_user::get_name_placeholders($user);
+        foreach ($placeholders as $field => $value) {
+            $data->{$field} = $value;
+        }
         $data->sitename  = format_string($site->fullname);
         $data->admin     = generate_email_signoff();
 

auth/oauth2/lang/en/auth_oauth2.php

@@ -25,7 +25,7 @@
 $string['accountexists'] = 'A user already exists on this site with this username. If this is your account, log in by entering your username and password and add it as a linked login via your preferences page.';
 $string['auth_oauth2description'] = 'OAuth 2 standards based authentication';
 $string['auth_oauth2settings'] = 'OAuth 2 authentication settings.';
-$string['confirmaccountemail'] = 'Hi {$a->fullname},
+$string['confirmaccountemail'] = 'Hi {$a->firstname},
 
 A new account has been requested at \'{$a->sitename}\'
 using your email address.
@@ -47,7 +47,7 @@ Please contact the site administrator immediately.';
 $string['confirmaccountemailsubject'] = '{$a}: account confirmation';
 $string['confirmationinvalid'] = 'The confirmation link is either invalid, or has expired. Please start the login process again to generate a new confirmation email.';
 $string['confirmationpending'] = 'This account is pending email confirmation.';
-$string['confirmlinkedloginemail'] = 'Hi {$a->fullname},
+$string['confirmlinkedloginemail'] = 'Hi {$a->firstname},
 
 A request has been made to link the {$a->issuername} login
 {$a->linkedemail} to your account at \'{$a->sitename}\'

auth/oauth2/tests/api_test.php

@@ -22,6 +22,8 @@ namespace auth_oauth2;
  * @package     auth_oauth2
  * @copyright   2017 Damyon Wiese
  * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ *
+ * @covers \auth_oauth2\api
  */
 class api_test extends \advanced_testcase {
 
@@ -227,4 +229,39 @@ class api_test extends \advanced_testcase {
         // Explicitly test the user is not yet confirmed.
         $this->assertEquals(0, $userdata->confirmed);
     }
+
+    /**
+     * Test case for checking the email greetings in OAuth2 confirmation emails.
+     */
+    public function test_email_greetings(): void {
+        $this->resetAfterTest();
+        $this->setAdminUser();
+
+        $issuer = \core\oauth2\api::create_standard_issuer('microsoft');
+
+        $userinfo = [];
+        $userinfo['username'] = 'apple';
+        $userinfo['email'] = 'apple@example.com';
+        $userinfo['firstname'] = 'Apple';
+        $userinfo['lastname'] = 'Fruit';
+        $sink = $this->redirectEmails(); // Make sure we are redirecting emails.
+        \auth_oauth2\api::send_confirm_account_email($userinfo, $issuer);
+        $result = $sink->get_messages();
+        $sink->close();
+        // Test greetings.
+        $this->assertStringContainsString('Hi ' . $userinfo['firstname'], quoted_printable_decode($result[0]->body));
+
+        $userinfo = [];
+        $userinfo['username'] = 'banana';
+        $userinfo['email'] = 'banana@example.com';
+        $userinfo['firstname'] = 'Banana';
+        $userinfo['lastname'] = 'Fruit';
+        $user = $this->getDataGenerator()->create_user();
+        $sink = $this->redirectEmails(); // Make sure we are redirecting emails.
+        \auth_oauth2\api::send_confirm_link_login_email($userinfo, $issuer, $user->id);
+        $result = $sink->get_messages();
+        $sink->close();
+        // Test greetings.
+        $this->assertStringContainsString('Hi ' . $user->firstname, quoted_printable_decode($result[0]->body));
+    }
 }

auth/oauth2/tests/auth_test.php

@@ -23,7 +23,7 @@ namespace auth_oauth2;
  * @category   test
  * @copyright  2019 Shamim Rezaie
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- * @coversDefaultClass \auth_oauth2\auth
+ * @covers \auth_oauth2\auth
  */
 class auth_test extends \advanced_testcase {
 
@@ -89,4 +89,15 @@ class auth_test extends \advanced_testcase {
         $extrauserinfo = $event->other['extrauserinfo'];
         $this->assertEquals($info, $extrauserinfo);
     }
+
+    /**
+     *  Test case for checking the email greetings in the password change information email.
+     */
+    public function test_email_greetings(): void {
+        $this->resetAfterTest();
+        $user = $this->getDataGenerator()->create_user(['auth' => 'oauth2']);
+        $auth = get_auth_plugin($user->auth);
+        $info = $auth->get_password_change_info($user);
+        $this->assertStringContainsString('Hi ' . $user->firstname, quoted_printable_decode($info['message']));
+    }
 }