Save submission alongside structured error

app/models/structured_error.rb

@@ -1,9 +1,10 @@
 class StructuredError < ActiveRecord::Base
   belongs_to :error_template
+  belongs_to :submission
   belongs_to :file, class_name: 'CodeOcean::File'
 
-  def self.create_from_template(template, message_buffer)
-    instance = self.create(error_template: template)
+  def self.create_from_template(template, message_buffer, submission)
+    instance = self.create(error_template: template, submission: submission)
     template.error_template_attributes.each do |attribute|
       StructuredErrorAttribute.create_from_template(attribute, instance, message_buffer)
     end

app/models/submission.rb

@@ -8,6 +8,7 @@ class Submission < ActiveRecord::Base
   belongs_to :exercise
 
   has_many :testruns
+  has_many :structured_errors
   has_many :comments, through: :files
 
   delegate :execution_environment, to: :exercise