Fix regression with POA missing cache (#14305)

### Description

Fixes regression introduced in #13922 with the advent of the BgsPowerOfAttorney AR model.

We were skipping our local db cache and always making BGS calls, which slowed the job down to take hours instead of minutes.

.reek.yml

@@ -88,7 +88,7 @@ detectors:
       - Seeds::Users#create_aod_user_and_tasks
       - SyncReviewsJob
       - TaskTimerJob
-      - UpdateCachedAppealsAttributesJob#assignees_for_vacols_id
+      - UpdateCachedAppealsAttributesJob
       - UserReporter#report_user_related_records
       - User#current_case_assignments_with_views
       - User#appeal_has_task_assigned_to_user?
@@ -143,6 +143,7 @@ detectors:
       - RequestIssue
       - BulkTaskReassignment
       - Task
+      - UpdateCachedAppealsAttributesJob
   TooManyConstants:
     exclude:
       - Fakes::BGSServicePOA

app/jobs/update_cached_appeals_attributes_job.rb

@@ -103,15 +103,15 @@ def cache_legacy_appeal_postgres_data(legacy_appeals)
     values_to_cache = legacy_appeals.map do |appeal|
       regional_office = RegionalOffice::CITIES[appeal.closest_regional_office]
       # bypass PowerOfAttorney model completely and always prefer BGS cache
-      bgs_poa = BgsPowerOfAttorney.new(file_number: appeal.veteran_file_number)
+      bgs_poa = fetch_bgs_power_of_attorney_by_file_number(appeal.veteran_file_number)
       {
         vacols_id: appeal.vacols_id,
         appeal_id: appeal.id,
         appeal_type: LegacyAppeal.name,
         closest_regional_office_city: regional_office ? regional_office[:city] : COPY::UNKNOWN_REGIONAL_OFFICE,
         closest_regional_office_key: regional_office ? appeal.closest_regional_office : COPY::UNKNOWN_REGIONAL_OFFICE,
         docket_type: appeal.docket_name, # "legacy"
-        power_of_attorney_name: bgs_poa.representative_name || appeal.representative_name,
+        power_of_attorney_name: (bgs_poa&.representative_name || appeal.representative_name),
         suggested_hearing_location: appeal.suggested_hearing_location&.formatted_location
       }
     end
@@ -128,6 +128,14 @@ def cache_legacy_appeal_postgres_data(legacy_appeals)
   end
   # rubocop:enable Metrics/MethodLength
 
+  def fetch_bgs_power_of_attorney_by_file_number(file_number)
+    return if file_number.blank?
+
+    BgsPowerOfAttorney.find_or_create_by_file_number(file_number)
+  rescue ActiveRecord::RecordInvalid # not found at BGS
+    BgsPowerOfAttorney.new(file_number: file_number)
+  end
+
   # rubocop:disable Metrics/MethodLength
   # rubocop:disable Metrics/AbcSize
   def cache_legacy_appeal_vacols_data(all_vacols_ids)