Use file template to generate new file content

app/controllers/code_ocean/files_controller.rb

@@ -10,6 +10,9 @@ module CodeOcean
 
     def create
       @file = CodeOcean::File.new(file_params)
+      if @file.file_template_id
+        @file.content = FileTemplate.find(@file.file_template_id).content
+      end
       authorize!
       create_and_respond(object: @file, path: proc { implement_exercise_path(@file.context.exercise, tab: 2) })
     end

app/controllers/concerns/file_parameters.rb

@@ -1,6 +1,6 @@
 module FileParameters
   def file_attributes
-    %w(content context_id feedback_message file_id file_type_id hidden id name native_file path read_only role weight)
+    %w(content context_id feedback_message file_id file_type_id hidden id name native_file path read_only role weight file_template_id)
   end
   private :file_attributes
 end

app/views/code_ocean/files/_form.html.slim

@@ -8,5 +8,8 @@
   .form-group
     = f.label(:file_type_id, t('activerecord.attributes.file.file_type_id'))
     = f.collection_select(:file_type_id, FileType.where(binary: false).order(:name), :id, :name, {selected: @exercise.execution_environment.file_type.try(:id)}, class: 'form-control')
+  .form-group
+    = f.label(:file_template_id, t('activerecord.attributes.file.file_template_id'))
+    = f.collection_select(:file_template_id, FileTemplate.all.order(:name), :id, :name, {}, class: 'form-control')
   = f.hidden_field(:context_id)
   .actions = render('shared/submit_button', f: f, object: CodeOcean::File.new)