DEV: Change uploads.filesize column to bigint (#14334)

This is necessary to allow for large file uploads via
the direct S3 upload mechanism, as we convert the external
file to an Upload record via ExternalUploadManager once
it is complete.

This will allow for files larger than 2,147,483,647 bytes (2.14GB)
to be referenced in the uploads table.

This is a table locking migration, but since it is not as highly
trafficked as posts, topics, or users, the disruption should be minimal.

db/migrate/20210914011037_change_uploads_filesize_to_bigint.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class ChangeUploadsFilesizeToBigint < ActiveRecord::Migration[6.1]
+  def change
+    change_column :uploads, :filesize, :bigint
+  end
+end