Align project files with CodeHarbor

Since both projects are developed together and by the same team, we also want to have the same code structure and utility methods available in both projects. Therefore, this commit changes many files, but without a functional change.

spec/models/code_ocean/file_spec.rb

@@ -2,7 +2,7 @@
 
 require 'rails_helper'
 
-describe CodeOcean::File do
+RSpec.describe CodeOcean::File do
   let(:file) { described_class.create.tap {|file| file.update(content: nil, hidden: nil, read_only: nil) } }
 
   it 'validates the presence of a file type' do