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/models/message.rb

@@ -37,12 +37,33 @@ class Message < ApplicationRecord
   include Liquidable
   NUMBER_OF_PERMITTED_ATTACHMENTS = 15
 
+  TEMPLATE_PARAMS_SCHEMA = {
+    'type': 'object',
+    'properties': {
+      'template_params': {
+        'type': 'object',
+        'properties': {
+          'name': { 'type': 'string' },
+          'category': { 'type': 'string' },
+          'language': { 'type': 'string' },
+          'namespace': { 'type': 'string' },
+          'processed_params': { 'type': 'object' }
+        },
+        'required': %w[name category language namespace processed_params]
+      }
+    }
+  }.to_json.freeze
+
   before_validation :ensure_content_type
 
   validates :account_id, presence: true
   validates :inbox_id, presence: true
   validates :conversation_id, presence: true
   validates_with ContentAttributeValidator
+  validates_with JsonSchemaValidator,
+                 schema: TEMPLATE_PARAMS_SCHEMA,
+                 attribute_resolver: ->(record) { record.additional_attributes }
+
   validates :content_type, presence: true
   validates :content, length: { maximum: 150_000 }