Tidy up code and remove duplicate method

- Move cache key to new method
- Memoize related_issue

app/models/error_tracking/project_error_tracking_setting.rb

@@ -140,15 +140,20 @@ module ErrorTracking
       Addressable::URI.join(api_url, '/').to_s
     end
 
-    def clear_cache(key_prefix)
-      return unless key_prefix
+    def clear_cache(resource_prefix)
+      raise 'No resource prefix provided' unless resource_prefix
 
-      klass_key = self.class.reactive_cache_key.call(self).join(':')
-      Rails.cache.delete_matched("#{klass_key}:#{key_prefix}*")
+      Rails.cache.delete_matched(cache_key(resource_prefix))
     end
 
     private
 
+    def cache_key(resource_prefix)
+      klass_key = self.class.reactive_cache_key.call(self).join(':')
+
+      "#{klass_key}:#{resource_prefix}*"
+    end
+
     def add_gitlab_issue_details(issue)
       issue.gitlab_commit = match_gitlab_commit(issue.first_release_version)
       issue.gitlab_commit_path = project_commit_path(project, issue.gitlab_commit) if issue.gitlab_commit

app/services/error_tracking/issue_update_service.rb

@@ -23,10 +23,9 @@ module ErrorTracking
     end
 
     def update_related_issue
-      issue = related_issue
-      return unless issue
+      return if related_issue.nil?
 
-      close_and_create_note(issue)
+      close_and_create_note(related_issue)
     end
 
     def clear_cache
@@ -54,10 +53,12 @@ module ErrorTracking
     end
 
     def related_issue
-      SentryIssueFinder
-        .new(project, current_user: current_user)
-        .execute(params[:issue_id])
-        &.issue
+      strong_memoize(:related_issue) do
+        SentryIssueFinder
+          .new(project, current_user: current_user)
+          .execute(params[:issue_id])
+          &.issue
+      end
     end
 
     def resolving?

app/services/system_note_service.rb

@@ -105,12 +105,6 @@ module SystemNoteService
     create_note(NoteSummary.new(issue, project, author, body, action: 'closed'))
   end
 
-  def close_after_error_tracking_resolve(issue, project, author)
-    body = _('resolved the corresponding error and closed the issue.')
-
-    create_note(NoteSummary.new(issue, project, author, body, action: 'closed'))
-  end
-
   def change_status(noteable, project, author, status, source = nil)
     ::SystemNotes::IssuablesService.new(noteable: noteable, project: project, author: author).change_status(status, source)
   end