Add metric to service ping if has defintion

  - Add user_auth_by_provider metric defintion
  as object with related json schema
  - Remove individual metrics definitions for
  user_auth_by_provider
  - Add tests for object metrics
  - A hash could be a metric, with this MR
  we change th meaning of a leaf in payload.
  - A metric is a leaf if it has a metric defintion

spec/support/shared_contexts/services/service_ping/stubbed_service_ping_metrics_definitions_shared_context.rb

@@ -7,7 +7,6 @@ RSpec.shared_context 'stubbed service ping metrics definitions' do
   let(:standard_metrics) do
     [
       metric_attributes('uuid', 'standard'),
-      metric_attributes('recorded_at', 'standard'),
       metric_attributes('settings.collected_data_categories', 'standard', 'object')
     ]
   end