Inconsistent schema - index

Add index_design_management_versions_on_author_id index

Changelog: fixed

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/349549

db/post_migrate/20220116175851_add_author_index_to_design_management_versions.rb

+# frozen_string_literal: true
+
+class AddAuthorIndexToDesignManagementVersions < Gitlab::Database::Migration[1.0]
+  TABLE = :design_management_versions
+  INDEX_NAME = 'index_design_management_versions_on_author_id'
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index TABLE, :author_id, where: 'author_id IS NOT NULL', name: INDEX_NAME
+  end
+
+  def down
+    remove_concurrent_index TABLE, :author_id, name: INDEX_NAME
+  end
+end

db/schema_migrations/20220116175851

+3fa0d827ab8051d270a13ae5facb1560a87f9f4fef81368b9fbb5d6291948721
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