preparations to replace session with lti_parameters object

db/migrate/20161214144837_create_lti_parameters.rb

@@ -2,9 +2,9 @@ class CreateLtiParameters < ActiveRecord::Migration
   def change
     create_table :lti_parameters do |t|
       t.string :external_user_id
-      t.string :consumer_id
-      t.string :exercise_id
-      t.text :lti_return_url
+      t.belongs_to :consumers
+      t.belongs_to :exercises
+      t.column :lti_parameters, :jsonb
 
       t.timestamps
     end

db/migrate/20161216130605_remove_lti_return_url_from_lti_parameter.rb

@@ -1,5 +0,0 @@
-class RemoveLtiReturnUrlFromLtiParameter < ActiveRecord::Migration
-  def change
-    remove_column :lti_parameters, :lti_return_url, :text
-  end
-end

db/migrate/20161216131239_add_lti_parameters_to_lti_parameter.rb

@@ -1,5 +0,0 @@
-class AddLtiParametersToLtiParameter < ActiveRecord::Migration
-  def change
-    add_column :lti_parameters, :lti_parameters, :json
-  end
-end