feat: Enable template variables in channel greeting messages (#6971)

app/helpers/email_helper.rb

@@ -10,4 +10,26 @@ module EmailHelper
   def normalize_email_with_plus_addressing(email)
     "#{email.split('@').first.split('+').first}@#{email.split('@').last}".downcase
   end
+
+  def parse_email_variables(conversation, email)
+    case email
+    when modified_liquid_content(email)
+      template = Liquid::Template.parse(modified_liquid_content(email))
+      template.render(message_drops(conversation))
+    when URI::MailTo::EMAIL_REGEXP
+      email
+    end
+  end
+
+  def modified_liquid_content(email)
+    # This regex is used to match the code blocks in the content
+    # We don't want to process liquid in code blocks
+    email.gsub(/`(.*?)`/m, '{% raw %}`\\1`{% endraw %}')
+  end
+
+  def message_drops(conversation)
+    {
+      'contact' => ContactDrop.new(conversation.contact)
+    }
+  end
 end