Validate course subject params before assigning course attributes

  It's easier to separate the parameter validation from the course
  validation in the Subjects controller. This commit covers all subject
  types including physics, modern languages, primary, secondary and
  further education

app/controllers/publish/courses/subjects_controller.rb

@@ -18,43 +18,44 @@ def continue
 
       def update
         authorize(provider)
-
-        if params[:course][:master_subject_id] == SecondarySubject.physics.id.to_s
-          course.update(master_subject_id: params[:course][:master_subject_id])
-          redirect_to(
-            engineers_teach_physics_publish_provider_recruitment_cycle_course_path(
-              @course.provider_code,
-              @course.recruitment_cycle_year,
-              @course.course_code,
-              course: { master_subject_id: SecondarySubject.physics.id.to_s, subjects_ids: selected_subject_ids }
+        if validate_subject_ids
+          if params[:course][:master_subject_id] == SecondarySubject.physics.id.to_s
+            course.update(master_subject_id: params[:course][:master_subject_id])
+            redirect_to(
+              engineers_teach_physics_publish_provider_recruitment_cycle_course_path(
+                @course.provider_code,
+                @course.recruitment_cycle_year,
+                @course.course_code,
+                course: { master_subject_id: SecondarySubject.physics.id.to_s, subjects_ids: selected_subject_ids }
+              )
             )
-          )
-
-        elsif selected_subject_ids.include?(modern_languages_subject_id.to_s) && validate_subject_ids
-          course.update(master_subject_id: params[:course][:master_subject_id])
-          redirect_to(
-            modern_languages_publish_provider_recruitment_cycle_course_path(
-              @course.provider_code,
-              @course.recruitment_cycle_year,
-              @course.course_code,
-              course: { subjects_ids: selected_subject_ids }
+
+          elsif selected_subject_ids.include?(modern_languages_subject_id.to_s)
+            course.update(master_subject_id: params[:course][:master_subject_id])
+            redirect_to(
+              modern_languages_publish_provider_recruitment_cycle_course_path(
+                @course.provider_code,
+                @course.recruitment_cycle_year,
+                @course.course_code,
+                course: { subjects_ids: selected_subject_ids }
+              )
             )
-          )
-
-        elsif course.errors.none? && course_subjects_form.save!
-          course_updated_message(section_key)
-          # TODO: move this to the form?
-          course.update(master_subject_id: params[:course][:master_subject_id])
-          course.update(name: course.generate_name)
-          course.update(campaign_name: nil) unless course.master_subject_id == SecondarySubject.physics.id
-
-          redirect_to(
-            details_publish_provider_recruitment_cycle_course_path(
-              @course.provider_code,
-              @course.recruitment_cycle_year,
-              @course.course_code
+
+          elsif course.errors.none? && course_subjects_form.save!
+            course_updated_message(section_key)
+            # TODO: move this to the form?
+            course.update(master_subject_id: params[:course][:master_subject_id])
+            course.update(name: course.generate_name)
+            course.update(campaign_name: nil) unless course.master_subject_id == SecondarySubject.physics.id
+
+            redirect_to(
+              details_publish_provider_recruitment_cycle_course_path(
+                @course.provider_code,
+                @course.recruitment_cycle_year,
+                @course.course_code
+              )
             )
-          )
+          end
         else
           @errors = @course.errors.messages
           course.master_subject_id = selected_master