Fix export size doubling from re-exporting prior export blobs (#2707)

* Exclude export/import blobs and attachments from account exports

Export and import file blobs were being assigned the account's
account_id (via the Current.account default), causing subsequent
exports to include previous export/import ZIP files in the data.
This roughly doubled the export size each time and made imports
fail with an IntegrityError on unrecognized "Account::Export"
record type.

Filter out blobs attached to Export/Import records in
BlobRecordSet, FileRecordSet, and a new AttachmentRecordSet.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Use STI base type for export blob exclusion filter

Rails polymorphic_name returns base_class.name for STI models,
so ActiveStorage stores record_type as "Export" rather than the
concrete subclass names. Filter on the base type accordingly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix export filtering for mixed-use Active Storage blobs

Exclude only internal-only blobs for account export metadata/file sets, scope attachment subqueries by account, and add regression coverage for blobs shared between user records and export attachments.

* Simplify export blob filtering

Exports always create fresh blobs, so a blob can never be legitimately
shared between an Export/Import and a real account record. Replace the
internal_only/external split with a single excluded_blob_ids subquery
and drop the contrived shared-blob test.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

app/models/account/data_transfer/active_storage/attachment_record_set.rb

@@ -0,0 +1,11 @@
+class Account::DataTransfer::ActiveStorage::AttachmentRecordSet < Account::DataTransfer::RecordSet
+  def initialize(account)
+    super(account: account, model: ::ActiveStorage::Attachment)
+  end
+
+  private
+    def records
+      ::ActiveStorage::Attachment.where(account: account)
+        .where.not(record_type: INTERNAL_RECORD_TYPES)
+    end
+end

app/models/account/data_transfer/active_storage/blob_record_set.rb

@@ -8,6 +8,14 @@ class Account::DataTransfer::ActiveStorage::BlobRecordSet < Account::DataTransfe
   end
 
   private
+    def records
+      ::ActiveStorage::Blob.where(account: account).where.not(id: excluded_blob_ids)
+    end
+
+    def excluded_blob_ids
+      ::ActiveStorage::Attachment.where(account: account, record_type: INTERNAL_RECORD_TYPES).select(:blob_id)
+    end
+
     def import_batch(files)
       batch_data = files.map do |file|
         data = load(file)

app/models/account/data_transfer/active_storage/file_record_set.rb

@@ -5,7 +5,11 @@ class Account::DataTransfer::ActiveStorage::FileRecordSet < Account::DataTransfe
 
   private
     def records
-      ::ActiveStorage::Blob.where(account: account)
+      ::ActiveStorage::Blob.where(account: account).where.not(id: excluded_blob_ids)
+    end
+
+    def excluded_blob_ids
+      ::ActiveStorage::Attachment.where(account: account, record_type: INTERNAL_RECORD_TYPES).select(:blob_id)
     end
 
     def export_record(blob)

app/models/account/data_transfer/manifest.rb

@@ -58,7 +58,7 @@ class Account::DataTransfer::Manifest
           ::Webhook::Delivery
         ),
         Account::DataTransfer::ActiveStorage::BlobRecordSet.new(account),
-        *build_record_sets(::ActiveStorage::Attachment),
+        Account::DataTransfer::ActiveStorage::AttachmentRecordSet.new(account),
         Account::DataTransfer::ActionText::RichTextRecordSet.new(account),
         Account::DataTransfer::ActiveStorage::FileRecordSet.new(account)
       ].then { set_importable_model_names(it) }

app/models/account/data_transfer/record_set.rb

@@ -3,6 +3,7 @@ class Account::DataTransfer::RecordSet
   class ConflictError < IntegrityError; end
 
   IMPORT_BATCH_SIZE = 100
+  INTERNAL_RECORD_TYPES = %w[Export Account::Import].freeze
 
   attr_accessor :importable_model_names
   attr_reader :account, :model, :attributes