chore: Support plus forwarding in email channel (#6482)

- Support for plus forwarding in the email addresses for email channels

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

app/finders/email_channel_finder.rb

@@ -1,4 +1,6 @@
 class EmailChannelFinder
+  include EmailHelper
+
   def initialize(email_object)
     @email_object = email_object
   end
@@ -7,7 +9,8 @@ class EmailChannelFinder
     channel = nil
     recipient_mails = @email_object.to.to_a + @email_object.cc.to_a
     recipient_mails.each do |email|
-      channel = Channel::Email.find_by('lower(email) = ? OR lower(forward_to_email) = ?', email.downcase, email.downcase)
+      normalized_email = normalize_email_with_plus_addressing(email)
+      channel = Channel::Email.find_by('lower(email) = ? OR lower(forward_to_email) = ?', normalized_email, normalized_email)
       break if channel.present?
     end
     channel

app/helpers/email_helper.rb

@@ -3,4 +3,11 @@ module EmailHelper
     domain = email.split('@').last
     domain.split('.').first
   end
+
+  # ref: https://www.rfc-editor.org/rfc/rfc5233.html
+  # This is not a  mandatory requirement for email addresses, but it is a common practice.
+  # john+test@xyc.com is the same as john@xyc.com
+  def normalize_email_with_plus_addressing(email)
+    "#{email.split('@').first.split('+').first}@#{email.split('@').last}".downcase
+  end
 end