feat(server): support comment notification type (#12924)

#### PR Dependency Tree


* **PR #12924** 👈
  * **PR #12925**

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Introduced comment and comment mention notifications, including email
notifications when users are mentioned or receive comments on documents.
* Added new email templates for comment and comment mention
notifications.
* Users can now control whether they receive comment-related emails via
a new user setting.

* **Bug Fixes**
  * None.

* **Documentation**
* Updated GraphQL schema documentation to reflect new notification types
and user settings.

* **Refactor**
* Streamlined and enhanced test coverage for notification and user
settings, including comment notifications.

* **Chores**
* Improved test setup and snapshot coverage for user settings and
notifications.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/schema.gql

@@ -1361,6 +1361,8 @@ type NotificationObjectTypeEdge {
 
 """Notification type"""
 enum NotificationType {
+  Comment
+  CommentMention
   Invitation
   InvitationAccepted
   InvitationBlocked
@@ -1933,6 +1935,9 @@ input UpdateUserInput {
 }
 
 input UpdateUserSettingsInput {
+  """Receive comment email"""
+  receiveCommentEmail: Boolean
+
   """Receive invitation email"""
   receiveInvitationEmail: Boolean
 
@@ -1993,6 +1998,9 @@ type UserQuotaUsageType {
 }
 
 type UserSettingsType {
+  """Receive comment email"""
+  receiveCommentEmail: Boolean!
+
   """Receive invitation email"""
   receiveInvitationEmail: Boolean!