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 @@ public static function send_confirm_link_login_email($userinfo, $issuer, $userid
         $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 @@ public static function send_confirm_account_email($userinfo, $issuer) {
         $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 @@
 $string['confirmaccountemailsubject'] = '{$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 @@
  * @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 @@ public function test_send_confirm_account_email(): void {
         // 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'] = '[email protected]';
+        $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'] = '[email protected]';
+        $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 @@
  * @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 @@ public function test_oauth2_complete_login(): void {
         $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']));
+    }
 }