Use Ruby syntax instead of SQL snippets for Testrun queries

app/controllers/flowr_controller.rb

@@ -6,7 +6,7 @@ class FlowrController < ApplicationController
     # get the latest submission for this user that also has a test run (i.e. structured_errors if applicable)
     submission = Submission.joins(:testruns)
       .where(submissions: {user_id: current_user.id, user_type: current_user.class.name})
-      .order('testruns.created_at DESC').first
+      .order(testruns: {created_at: :desc}).first
 
     # Return if no submission was found
     if submission.blank? || @embed_options[:disable_hints] || @embed_options[:hide_test_results]

app/helpers/statistics_helper.rb

@@ -79,7 +79,7 @@ module StatisticsHelper
       {
         key: 'container_requests_per_minute',
           name: t('statistics.entries.exercises.container_requests_per_minute'),
-          data: (Testrun.where('created_at >= ?', DateTime.now - 1.hour).count.to_f / 60).round(2),
+          data: (Testrun.where(created_at: DateTime.now - 1.hour..).count.to_f / 60).round(2),
           unit: '/min',
       },
       {