Word a provider account's first-password email as setting, not resetting

Since GHSA-4r8h-mwfm-f5f4, an account that signs in through a provider
gets its first password only from the reset link emailed to it. That
email said "you are receiving this because we received a password reset
request", to somebody who never had a password and may well ignore it.

ResetPasswordNotification now takes firstPassword, which
User::sendPasswordResetNotification() sets for an AuthSource::Social
account: "Set your password", what the link is for, and that nothing
changes if they did not ask. It is not taken from the customisable reset
template, whose text is written about resetting. Accounts with a password
get the reset email exactly as before.

app/Models/User.php

@@ -152,7 +152,10 @@ class User extends Authenticatable implements HasLocalePreference
      */
     public function sendPasswordResetNotification($token)
     {
-        $this->notify(new ResetPasswordNotification($token));
+        // An account that signs in through a provider has never had a
+        // password here, so its link sets the first one rather than
+        // resetting anything (PasswordController::sendLink).
+        $this->notify(new ResetPasswordNotification($token, firstPassword: $this->auth_source === AuthSource::Social));
     }
 
     /**

app/Modules/Identity/Notifications/ResetPasswordNotification.php

@@ -27,6 +27,7 @@ class ResetPasswordNotification extends Notification implements ShouldQueue
 
     public function __construct(
         public readonly string $token,
+        public readonly bool $firstPassword = false,
     ) {}
 
     /**
@@ -46,6 +47,20 @@ class ResetPasswordNotification extends Notification implements ShouldQueue
 
         $expireMinutes = (int) config('auth.passwords.'.config('auth.defaults.passwords').'.expire');
 
+        // The same link, for an account that signs in through a provider and
+        // has never had a password: this is now the only way it gets one, so
+        // an email that speaks of a reset nobody asked for is one people
+        // ignore. Not taken from the customisable reset template for the
+        // same reason, since that text is written about resetting.
+        if ($this->firstPassword) {
+            return (new MailMessage)
+                ->subject(__('Set your password'))
+                ->line(__('Use the button below to choose a password for your account. Until now you have signed in through a connected account, such as Google or Microsoft.'))
+                ->action(__('Set a password'), $url)
+                ->line(__('This link will expire in :count minutes.', ['count' => $expireMinutes]))
+                ->line(__('If you did not ask for this, no further action is required: you can keep signing in the way you do now.'));
+        }
+
         if (($override = $this->overrideOrNull(EmailTemplateSlot::PasswordReset)) !== null) {
             return $this->mailFromOverride($override, [':count' => (string) $expireMinutes])
                 ->action(__('Reset Password'), $url);

tests/Feature/Identity/ProviderAccountPasswordTest.php

@@ -106,6 +106,32 @@ test('using the link signs out the session that asked for it', function () {
     $this->assertGuest();
 });
 
+test('the email to a provider account is about setting a first password, not a reset', function () {
+    Notification::fake();
+    $user = providerAccount();
+
+    $this->actingAs($user)->post('/settings/password/link');
+
+    Notification::assertSentTo($user, ResetPasswordNotification::class, function (ResetPasswordNotification $notification) use ($user): bool {
+        $mail = $notification->toMail($user);
+
+        return $mail->subject === __('Set your password')
+            && $mail->actionText === __('Set a password')
+            && ! str_contains(implode(' ', $mail->introLines), 'reset');
+    });
+});
+
+test('an account with a password still gets the reset email', function () {
+    Notification::fake();
+    $user = User::factory()->create();
+
+    $this->post('/forgot-password', ['email' => $user->email]);
+
+    Notification::assertSentTo($user, ResetPasswordNotification::class, function (ResetPasswordNotification $notification) use ($user): bool {
+        return $notification->toMail($user)->subject === __('Reset Password Notification');
+    });
+});
+
 test('an account that already has a password uses the form, not a link', function () {
     Notification::fake();
     $user = User::factory()->create();