Redirect users after sign in to their desired page

app/controllers/application_controller.rb

@@ -127,11 +127,14 @@ class ApplicationController < ActionController::Base
     respond_to do |format|
       format.any do
         # Prevent redirect loop
-        if request.url == request.referer
+        if request.url == request.referer || request.referer&.match?(sign_in_path)
           redirect_to :root, alert: message
         # Redirect to main domain if the request originated from our render_host
         elsif request.path == '/' && request.host == RENDER_HOST
           redirect_to Rails.application.config.action_mailer.default_url_options, allow_other_host: true
+        elsif current_user.nil? && status == :unauthorized
+          session[:return_to_url] = request.fullpath if current_user.nil?
+          redirect_to sign_in_path, alert: t('application.not_signed_in')
         else
           redirect_back fallback_location: :root, allow_other_host: false, alert: message
         end

app/views/sessions/new.html.slim

@@ -1,5 +1,13 @@
 h1 = t('.headline')
 
+.lead
+  .card.border-info-subtle.mb-3
+    .card-header
+      i.fa-solid.fa-circle-info.text-info
+      strong.text-info
+        => t('.instructors_only')
+      = t('.instructors_only_explanation', application_name:)
+
 = form_tag(sessions_path) do
   .mb-3
     = label_tag(:email, t('activerecord.attributes.internal_user.email'))