Add StudyGroup to submissions and show it for submissions and RfCs

Also take care of deleting a StudyGroup for existing submissions

app/controllers/concerns/lti.rb

@@ -168,6 +168,7 @@ module Lti
     end
     group.users |= [@current_user] # add current user if not already member of the group
     group.save
+    session[:study_group_id] = group.id
   end
 
   def set_embedding_options

app/controllers/concerns/submission_parameters.rb

@@ -16,7 +16,8 @@ module SubmissionParameters
       current_user_id = current_user.id
       current_user_class_name = current_user.class.name
     end
-    submission_params = params[:submission].present? ? params[:submission].permit(:cause, :exercise_id, files_attributes: file_attributes).merge(user_id: current_user_id, user_type: current_user_class_name) : {}
+    # The study_group_id might not be present in the session (e.g. for internal users), resulting in session[:study_group_id] = nil which is intended.
+    submission_params = params[:submission].present? ? params[:submission].permit(:cause, :exercise_id, files_attributes: file_attributes).merge(user_id: current_user_id, user_type: current_user_class_name, study_group_id: session[:study_group_id]) : {}
     reject_illegal_file_attributes!(submission_params)
     submission_params
   end

app/controllers/request_for_comments_controller.rb

@@ -83,17 +83,10 @@ class RequestForCommentsController < ApplicationController
     authorize!
   end
 
-  # GET /request_for_comments/new
-  def new
-    @request_for_comment = RequestForComment.new
-    authorize!
-  end
-
   # GET /request_for_comments/1/edit
   def edit
   end
 
-  # POST /request_for_comments
   # POST /request_for_comments.json
   def create
     # Consider all requests as JSON
@@ -149,8 +142,8 @@ class RequestForCommentsController < ApplicationController
 
     # Never trust parameters from the scary internet, only allow the white list through.
     def request_for_comment_params
-      # we are using the current_user.id here, since internal users are not able to create comments. The external_user.id is a primary key and does not require the consumer_id to be unique.
-      params.require(:request_for_comment).permit(:exercise_id, :file_id, :question, :requested_at, :solved, :submission_id).merge(user_id: current_user.id, user_type: current_user.class.name)
+      # The study_group_id might not be present in the session (e.g. for internal users), resulting in session[:study_group_id] = nil which is intended.
+      params.require(:request_for_comment).permit(:exercise_id, :file_id, :question, :requested_at, :solved, :submission_id).merge(user_id: current_user.id, user_type: current_user.class.name, study_group_id: session[:study_group_id])
     end
 
     def comment_params