Allow platform admins and internal users to switch their current study group

app/controllers/sessions_controller.rb

@@ -13,6 +13,8 @@ class SessionsController < ApplicationController
 
   def create
     if login(params[:email], params[:password], params[:remember_me])
+      # We set the user's default study group to the "internal" group (no external id) for the given consumer.
+      session[:study_group_id] = current_user.study_groups.find_by(external_id: nil)&.id
       redirect_back_or_to(:root, notice: t('.success'))
     else
       flash.now[:danger] = t('.failure')