Implement support for some basic embed options for work sheets via LTI

This commit also fixes an issue with the flash messages being positioned too high and displayed for too long

app/controllers/concerns/lti.rb

@@ -22,6 +22,7 @@ module Lti
     if (exercise_id.nil?)
       session.delete(:consumer_id)
       session.delete(:external_user_id)
+      session.delete(:embed_options)
     else
       LtiParameter.where(consumers_id: consumer_id,
                          external_users_id: user_id,
@@ -133,6 +134,26 @@ module Lti
   end
   private :set_current_user
 
+  def set_embedding_options
+    @embed_options = {}
+    [:hide_navbar,
+     :hide_exercise_description,
+     :disable_run,
+     :disable_score,
+     :disable_rfc,
+     :disable_interventions,
+     :hide_sidebar,
+     :read_only,
+     :hide_test_results,
+     :disable_hints].each do |option|
+      value = params["custom_embed_options_#{option}".to_sym] == 'true'
+      # Optimize storage and save only those that are true, the session cookie is limited to 4KB
+      @embed_options[option] = value if value.present?
+    end
+    session[:embed_options] = @embed_options
+  end
+  private :set_embedding_options
+
   def store_lti_session_data(options = {})
     lti_parameters = LtiParameter.find_or_create_by(consumers_id: options[:consumer].id,
                                                     external_users_id: @current_user.id,