fix: validate template_params for WhatsApp (#6881)

- Add JsonSchemaValidator, which takes a declarative schema and validates it for a given property.
- Add specs for JsonSchemaValidator
- Enable the validator for template_params

app/services/whatsapp/send_on_whatsapp_service.rb

@@ -28,13 +28,14 @@ class Whatsapp::SendOnWhatsappService < Base::SendOnChannelService
     message.update!(source_id: message_id) if message_id.present?
   end
 
+  # rubocop:disable Metrics/CyclomaticComplexity
   def processable_channel_message_template
     if template_params.present?
       return [
         template_params['name'],
         template_params['namespace'],
         template_params['language'],
-        template_params['processed_params'].map { |_, value| { type: 'text', text: value } }
+        template_params['processed_params']&.map { |_, value| { type: 'text', text: value } }
       ]
     end
 
@@ -55,6 +56,7 @@ class Whatsapp::SendOnWhatsappService < Base::SendOnChannelService
     end
     [nil, nil, nil, nil]
   end
+  # rubocop:enable Metrics/CyclomaticComplexity
 
   def template_match_object(template)
     body_object = validated_body_object(template)