FEATURE: Allow specific groups to view raw email (#26003)

When a post is created by an incoming email, we show
an envelope icon on it which then opens a modal with the
raw email contents. Previously this was staff (admin+mod)
only, but now this commit adds the `view_raw_email_allowed_groups`
site setting, so any group can be added to give users permission
to see this.

app/assets/javascripts/discourse/app/lib/transform-post.js

@@ -130,7 +130,7 @@ export default function transformPost(
     postType === postTypes.small_action || post.action_code === "split_topic";
   postAtts.canBookmark = !!currentUser;
   postAtts.canManage = currentUser && currentUser.get("canManageTopic");
-  postAtts.canViewRawEmail = currentUser && currentUser.staff;
+  postAtts.canViewRawEmail = currentUser && currentUser.can_view_raw_email;
   postAtts.canArchiveTopic = !!details.can_archive_topic;
   postAtts.canCloseTopic = !!details.can_close_topic;
   postAtts.canSplitMergeTopic = !!details.can_split_merge_topic;

app/serializers/current_user_serializer.rb

@@ -75,7 +75,8 @@ class CurrentUserSerializer < BasicUserSerializer
              :use_experimental_topic_bulk_actions?,
              :use_experimental_topic_bulk_actions?,
              :use_admin_sidebar,
-             :glimmer_header_enabled?
+             :glimmer_header_enabled?,
+             :can_view_raw_email
 
   delegate :user_stat, to: :object, private: true
   delegate :any_posts, :draft_count, :pending_posts_count, :read_faq?, to: :user_stat
@@ -316,4 +317,8 @@ class CurrentUserSerializer < BasicUserSerializer
   def use_experimental_topic_bulk_actions?
     scope.user.in_any_groups?(SiteSetting.experimental_topic_bulk_actions_enabled_groups_map)
   end
+
+  def can_view_raw_email
+    scope.user.in_any_groups?(SiteSetting.view_raw_email_allowed_groups_map)
+  end
 end