fix specs, add migrator

Rakefile

@@ -13,6 +13,7 @@ Rake.application.rake_require "fa"
 Rake.application.rake_require "e621"
 Rake.application.rake_require "twitter"
 Rake.application.rake_require "ib"
+Rake.application.rake_require "blob_file"
 
 task set_ar_stdout: :environment do
   ActiveRecord::Base.logger = Logger.new($stdout)
@@ -57,24 +58,6 @@ task periodic_tasks: %i[environment set_logger_stdout] do
   loop { sleep 10 }
 end
 
-namespace :blob_entries do
-  task export_samples: :environment do
-    limit = ENV["limit"]&.to_i || raise("need 'limit' (num)")
-    outfile =
-      ENV["outfile"] || raise("need 'outfile' (file path, .json encoded)")
-    BlobEntrySampleExporter.new.export_samples(limit, outfile)
-  end
-  task import_samples: :environment do
-    infile = ENV["infile"] || raise("need 'infile' (file path, .json encoded)")
-    BlobEntrySampleExporter.new.import_samples(infile)
-  end
-  task migrate_entries: :environment do
-    start_at = ENV["start_at"]
-    batch_size = ENV["batch_size"]&.to_i || 64
-    BlobEntrySampleExporter.new.migrate_blob_entries(start_at, batch_size)
-  end
-end
-
 namespace :db_sampler do
   task export: :environment do
     url_names = ENV["url_names"] || raise("need 'url_names' (comma-separated)")