add documents preview endpoint

app/controllers/api/submission_documents_controller.rb

@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module Api
+  class SubmissionDocumentsController < ApiBaseController
+    load_and_authorize_resource :submission
+
+    def index
+      documents =
+        if @submission.submitters.all?(&:completed_at?)
+          last_submitter = @submission.submitters.max_by(&:completed_at)
+
+          if last_submitter.documents_attachments.blank?
+            last_submitter.documents_attachments = Submissions::EnsureResultGenerated.call(submitter)
+          end
+
+          last_submitter.documents_attachments
+        else
+          values_hash = Submissions::GeneratePreviewAttachments.build_values_hash(@submission)
+
+          if @submission.preview_documents.present? &&
+             @submission.preview_documents.all? { |s| s.metadata['values_hash'] == values_hash }
+            @submission.preview_documents
+          else
+            ApplicationRecord.no_touching do
+              @submission.preview_documents.each(&:destroy)
+            end
+
+            Submissions::GeneratePreviewAttachments.call(@submission, values_hash:)
+          end
+        end
+
+      ActiveRecord::Associations::Preloader.new(
+        records: documents,
+        associations: [:blob]
+      ).call
+
+      render json: {
+        id: @submission.id,
+        documents: documents.map do |attachment|
+          { name: attachment.filename.base, url: ActiveStorage::Blob.proxy_url(attachment.blob) }
+        end
+      }
+    end
+  end
+end