Allow to use simple templates in hints to embed captured error values

app/models/structured_error.rb

@@ -3,11 +3,21 @@ class StructuredError < ActiveRecord::Base
   belongs_to :submission
   belongs_to :file, class_name: 'CodeOcean::File'
 
+  has_many :structured_error_attributes
+
   def self.create_from_template(template, message_buffer, submission)
     instance = self.create(error_template: template, submission: submission)
-    template.error_template_attributes.each do |attribute|
+    template.error_template_attributes.each do | attribute |
       StructuredErrorAttribute.create_from_template(attribute, instance, message_buffer)
     end
     instance
   end
+
+  def hint
+    content = error_template.hint
+    structured_error_attributes.each do | attribute |
+      content.sub! "{{#{attribute.error_template_attribute.key}}}", attribute.value if attribute.match
+    end
+    content
+  end
 end