fix: Case insensitive email match (#6760)

Fixes: https://linear.app/chatwoot/issue/CW-1354/email-id-case-sensitive

Co-authored-by: Sojan <sojan@pepalo.com>

app/models/user.rb

@@ -106,6 +106,10 @@ class User < ApplicationRecord
 
   scope :order_by_full_name, -> { order('lower(name) ASC') }
 
+  before_validation do
+    self.email = email.try(:downcase)
+  end
+
   def send_devise_notification(notification, *args)
     devise_mailer.with(account: Current.account).send(notification, self, *args).deliver_later
   end