extract Work#oral_history_number to DRY look up of external_id for OH number

app/components/work_show_info_component.rb

@@ -172,7 +172,7 @@ def oral_history_interviewer_profiles
   end
 
   def oral_history_number
-    @oral_history_number ||= work.external_id.find { |id| id.category == "interview"}&.value
+    @oral_history_number ||= work.oral_history_number
   end
 
   private

app/controllers/admin/works_controller.rb

@@ -273,7 +273,7 @@ def remove_searchable_transcript_source
   # GET /admin/works/ab2323ac/download_searchable_transcript_source
   def download_searchable_transcript_source
     authorize! :read, @work
-    id = @work.external_id.find { |id| id.category == "interview" }&.value
+    id = @work.oral_history_number
     id ||= @work.friendlier_id
     filename =  "#{id}_transcript.txt"
     send_data @work.oral_history_content!.searchable_transcript_source,

app/models/oral_history_request.rb

@@ -25,18 +25,12 @@ class OralHistoryRequest < ApplicationRecord
   end
 
   def oral_history_number
-    return nil if self.work.external_id.nil?
-    oh_id =  self.work.external_id.find {|id| id.attributes["category"] == "interview"}
-    return nil if oh_id.nil?
-    oh_id.attributes['value']
+    self.work.oral_history_number
   end
 
-
   # delegate to oral_history_requester, or while we're migrating default to
   # local attributes
   def requester_email
     oral_history_requester&.email
   end
-
-
 end

app/models/work.rb

@@ -132,6 +132,11 @@ def has_text_extraction?
     ocr_requested? || pdf_text_extraction?
   end
 
+  # Does not cache, looks up everytime, first external_id with category "interview", if present
+  def oral_history_number
+    self.external_id&.find { |id| id.category == "interview" }&.value
+  end
+
   # With one pg recursive CTE find _all_ descendent members, through
   # multiple levels.
   #

app/presenters/citable_attributes.rb

@@ -581,9 +581,7 @@ def archive_location
     end
 
     def interview_id
-      interview_ids = CitableAttributes::work_lookup(work, "external_id", "interview")
-      return nil if interview_ids.blank?
-      interview_ids.first
+      work.oral_history_number
     end
 
   end

lib/tasks/data_fixes/add_transcripts_to_oral_histories.rake

@@ -33,7 +33,7 @@ namespace :scihist do
           end
         end
 
-        accession_num =  w.external_id.find { |id| id.category == "interview" }&.value
+        accession_num =  w.oral_history_number
         unless accession_num
           progress_bar.log("ERROR: #{w.title}: no accession number.")
           progress_bar.increment