Put owner and participating people first

app/services/projects/participants_service.rb

 module Projects
   class ParticipantsService < BaseService
     def execute(note_type, note_id)
+      @target = get_target(note_type, note_id)
       participating =
         if note_type && note_id
           participants_in(note_type, note_id)
@@ -8,35 +9,43 @@ module Projects
           []
         end
       project_members = sorted(project.team.members)
-      participants = all_members + groups + project_members + participating
+      participants = target_owner + participating + all_members + groups + project_members
       participants.uniq
     end
 
+    def get_target(type, id)
+      case type
+      when "Issue"
+        project.issues.find_by_iid(id)
+      when "MergeRequest"
+        project.merge_requests.find_by_iid(id)
+      when "Commit"
+        project.commit(id)
+      end
+    end
+
+    def target_owner
+      [{
+        name: @target.author.name,
+        username: @target.author.username
+      }]
+    end
+
     def participants_in(type, id)
-      target = 
-        case type
-        when "Issue"
-          project.issues.find_by_iid(id)
-        when "MergeRequest"
-          project.merge_requests.find_by_iid(id)
-        when "Commit"
-          project.commit(id)
-        end
-        
-      return [] unless target
+      return [] unless @target
 
-      users = target.participants(current_user)
+      users = @target.participants(current_user)
       sorted(users)
     end
 
     def sorted(users)
-      users.uniq.to_a.compact.sort_by(&:username).map do |user| 
+      users.uniq.to_a.compact.sort_by(&:username).map do |user|
         { username: user.username, name: user.name }
       end
     end
 
     def groups
-      current_user.authorized_groups.sort_by(&:path).map do |group| 
+      current_user.authorized_groups.sort_by(&:path).map do |group|
         count = group.users.count
         { username: group.path, name: group.name, count: count }
       end