feat: Add liquid template support for WhatsApp template parameters (#12227)

Extends liquid template processing to WhatsApp `template_params`,
allowing dynamic variable substitution in template parameter values.

Users can now use liquid variables in WhatsApp template parameters:

```
{
  "template_params": {
    "name": "greet",
    "category": "MARKETING",
    "language": "en",
    "processed_params": {
      "body": {
        "customer_name": "{{contact.name}}",
        "customer_email": "{{contact.email | default: 'no-email@example.com'}}"
      }
    }
  }
}

```

When the message is saved, {{contact.name}} gets replaced with the
actual contact name.

Supported Variables

- {{contact.name}}, {{contact.email}}, {{contact.phone_number}}
- {{agent.name}}, {{agent.first_name}}
- {{account.name}}, {{inbox.name}}
- {{conversation.display_id}}
- Custom attributes: {{contact.custom_attribute.key_name}}
- Liquid filters: {{ contact.email | default: "fallback@example.com" }}

app/models/concerns/liquidable.rb

@@ -3,6 +3,7 @@ module Liquidable
 
   included do
     before_create :process_liquid_in_content
+    before_create :process_liquid_in_template_params
   end
 
   private
@@ -35,4 +36,61 @@ module Liquidable
     # We don't want to process liquid in code blocks
     content.gsub(/`(.*?)`/m, '{% raw %}`\\1`{% endraw %}')
   end
+
+  def process_liquid_in_template_params
+    return unless template_params_present? && liquid_processable_template_params?
+
+    processed_params = process_liquid_in_hash(template_params_data['processed_params'])
+
+    # Update the additional_attributes with processed template_params
+    self.additional_attributes = additional_attributes.merge(
+      'template_params' => template_params_data.merge('processed_params' => processed_params)
+    )
+  rescue Liquid::Error
+    # If there is an error in the liquid syntax, we don't want to process it
+  end
+
+  def template_params_present?
+    additional_attributes&.dig('template_params', 'processed_params').present?
+  end
+
+  def liquid_processable_template_params?
+    message_type == 'outgoing' || message_type == 'template'
+  end
+
+  def template_params_data
+    additional_attributes['template_params']
+  end
+
+  def process_liquid_in_hash(hash)
+    return hash unless hash.is_a?(Hash)
+
+    hash.transform_values { |value| process_liquid_value(value) }
+  end
+
+  def process_liquid_value(value)
+    case value
+    when String
+      process_liquid_string(value)
+    when Hash
+      process_liquid_in_hash(value)
+    when Array
+      process_liquid_array(value)
+    else
+      value
+    end
+  end
+
+  def process_liquid_array(array)
+    array.map { |item| process_liquid_value(item) }
+  end
+
+  def process_liquid_string(string)
+    return string if string.blank?
+
+    template = Liquid::Template.parse(string)
+    template.render(message_drops)
+  rescue Liquid::Error
+    string
+  end
 end