feat: Support Regex validation for custom attributes (#7856)

This allows a user to add/update a custom regex and a cue while defining custom attributes(Only applicable for type- text).
While adding/editing custom attributes, the values are validated against the attribute definition regex, and if it is incorrect, a cue message or default error message is shown and restricts invalid values from being saved.

Fixes: #6866

spec/jobs/inboxes/update_widget_pre_chat_custom_fields_job_spec.rb

@@ -11,7 +11,9 @@ RSpec.describe Inboxes::UpdateWidgetPreChatCustomFieldsJob do
   pre_chat_message = 'Share your queries here.'
   custom_attribute = {
     'attribute_key' => 'developer_id',
-    'attribute_display_name' => 'Developer Number'
+    'attribute_display_name' => 'Developer Number',
+    'regex_pattern' => '^[0-9]*',
+    'regex_cue' => 'It should be only digits'
   }
   let!(:account) { create(:account) }
   let!(:web_widget) do
@@ -23,7 +25,8 @@ RSpec.describe Inboxes::UpdateWidgetPreChatCustomFieldsJob do
       described_class.perform_now(account, custom_attribute)
       expect(web_widget.reload.pre_chat_form_options['pre_chat_fields']).to eq [
         { 'label' => 'Developer Number', 'name' => 'developer_id', 'placeholder' => 'Developer Number',
-          'values' => nil }, { 'label' => 'Full Name', 'name' => 'full_name' }
+          'values' => nil, 'regex_pattern' => '^[0-9]*', 'regex_cue' => 'It should be only digits' },
+        { 'label' => 'Full Name', 'name' => 'full_name' }
       ]
     end
   end